Boyko Borissov, former Bulgarian Prime Minister and leader of centre-right GERB party leaves the General Directorate National Police after he was summoned for questioning, in Sofia, Bulgaria, July 15, 2021. REUTERS/Spasiyana Sergieva

Boyko Borissov, former Bulgarian Prime Minister and leader of centre-right GERB party leaves the General Directorate National Police after he was summoned for questioning, in Sofia, Bulgaria, July 15, 2021. REUTERS/Spasiyana Sergieva

Boyko Borissov, former Bulgarian Prime Minister and leader of centre-right GERB party enters the General Directorate National Police after he was summoned for questioning, in Sofia, Bulgaria, July 15, 2021. REUTERS/Spasiyana Sergieva

Boyko Borissov, former Bulgarian Prime Minister and leader of centre-right GERB party, speaks during a news conference in Sofia, Bulgaria, July 12, 2021. REUTERS/Stoyan Nenov

Boyko Borissov, former Bulgarian Prime Minister and leader of centre-right GERB party, speaks during a news conference in Sofia, Bulgaria, July 12, 2021. REUTERS/Stoyan Nenov

Former Bulgarian Prime Minister Boyko Borissov speaks to the media during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov votes during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

A man wearing a t-shirt with an image of former Bulgarian Prime Minister Boyko Borissov walks as he votes during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov looks on after voting during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov votes during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov drives a car as he leaves after voting during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov votes during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov leaves after voting during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Former Bulgarian Prime Minister Boyko Borissov votes during a snap parliamentary election, at a polling station in Sofia, Bulgaria, July 11, 2021. REUTERS/Spasiyana Sergieva

Boyko Borissov, former Bulgarian Prime Minister and leader of centre-right GERB party walks during an election rally in Kardzhali, Bulgaria, July 5, 2021. Picture taken July 5, 2021. REUTERS/Stoyan Nenov

Boyko Borissov, former Bulgarian Prime Minister and leader of the centre-right GERB party speaks during an election rally in Kardzhali, Bulgaria, July 5, 2021. REUTERS/Stoyan Nenov

Boyko Borissov, former Bulgarian Prime Minister and leader of the centre-right GERB party attends an election rally in Kardzhali, Bulgaria, July 5, 2021. REUTERS/Stoyan Nenov

Boyko Borissov, former Bulgarian Prime Minister and leader of the centre-right GERB party poses for a picture with a supporter during an election rally in Kardzhali, Bulgaria, July 5, 2021. REUTERS/Stoyan Nenov

Boyko Borissov, former Bulgarian Prime Minister and leader of the centre-right GERB party, gestures during an election rally in Kardzhali, Bulgaria, July 5, 2021. REUTERS/Stoyan Nenov

A Bulgarian army tank fires during the "Strike Back 21" military drill in Koren training grounds, Bulgaria, June 4, 2021. Armed personnel from Greece, Romania and Bulgaria take part in the drill. REUTERS/Stoyan Nenov

A Bulgarian fiighter jet fires during the "Strike Back 21" military drill in Koren training grounds, Bulgaria, June 4, 2021. Armed personnel from Greece, Romania and Bulgaria take part in the drill. REUTERS/Stoyan Nenov

Soldiers from the Bulgarian army fire during the "Strike Back 21" military drill in Koren training grounds, Bulgaria, June 4, 2021. Armed personnel from Greece, Romania and Bulgaria take part in the drill. REUTERS/Stoyan Nenov

Portugal's President Marcelo Rebelo de Sousa and his Bulgarian counterpart Rumen Radev attend an official welcoming ceremony at the Tomb of Unknown Soldier in Sofia, Bulgaria, June 2, 2021. REUTERS/Stoyan Nenov

Portugal's President Marcelo Rebelo de Sousa talks to his Bulgarian counterpart Rumen Radev during an official welcoming ceremony at the Tomb of Unkown Soldier in Sofia, Bulgaria, June 2, 2021. REUTERS/Stoyan Nenov

North Macedonian President Stevo Pendarovski and Bulgarian President Rumen Radev get on Bulgarian presidential airplane at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril, in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski and Bulgarian President Rumen Radev get on Bulgarian presidential airplane at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril, in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski (L) meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski (L) meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

North Macedonian President Stevo Pendarovski (L) meets Bulgarian President Rumen Radev at Skopje airport ahead of a joint trip to Rome to visit the grave of St Cyril in Skopje, North Macedonia May 26, 2021. REUTERS/Ognen Teofilovski

Bulgarian President Rumen Radev departs from a face-to-face EU summit in Brussels, Belgium May 25, 2021. REUTERS/Johanna Geron/Pool

Bulgarian President Rumen Radev arrives at the second day of a special EU summit in Brussels, Belgium May 25, 2021. Olivier Hoslet/Pool via REUTERS

Bulgarian President Rumen Radev arrives at the second day of a special EU summit in Brussels, Belgium May 25, 2021. Olivier Hoslet/Pool via REUTERS

Bulgarian tourists, Tatiana Vasileva and her friend, tour the El Jem's amphitheatre, a UNESCO World Heritage Site built in the late 3rd century, in El Jem, amid the coronavirus disease (COVID-19) outbreak, Tunisia, May 20, 2021. Picture taken May 20, 2021. REUTERS/Angus McDowall

Bulgarian tourists, Tatiana Vasileva and her friend, are pictured at the El Jem's amphitheatre, a UNESCO World Heritage Site built in the late 3rd century, in El Jem, amid the coronavirus disease (COVID-19) outbreak, Tunisia, May 20, 2021. Picture taken May 20, 2021. REUTERS/Angus McDowall

A man attends the celebrations of Victory Day, which marks the anniversary of the victory over Nazi Germany in World War Two, in Sofia, Bulgaria, May 9, 2021. REUTERS/Spasiyana Sergieva

A woman holds Russian flag, as she attends the celebrations of Victory Day, which marks the anniversary of the victory over Nazi Germany in World War Two, in Sofia, Bulgaria, May 9, 2021. REUTERS/Spasiyana Sergieva

People attend the celebrations of Victory Day, which marks the anniversary of the victory over Nazi Germany in World War Two, in Sofia, Bulgaria, May 9, 2021. REUTERS/Spasiyana Sergieva

A World War Two veteran attends the celebrations of Victory Day, which marks the anniversary of the victory over Nazi Germany, in Sofia, Bulgaria, May 9, 2021. REUTERS/Spasiyana Sergieva

Bulgarian President Rumen Radev looks on before making a statement announcing parliamentary snap election, in Sofia, Bulgaria, May 5, 2021. REUTERS/Stoyan Nenov

Bulgarian President Rumen Radev makes a statement announcing parliamentary snap election, in Sofia, Bulgaria, May 5, 2021. REUTERS/Stoyan Nenov

Bulgarian President Rumen Radev makes a statement announcing a parliamentary snap election, in Sofia, Bulgaria, May 5, 2021. REUTERS/Stoyan Nenov

Bulgarian President Rumen Radev gives a mandate to form a new government to former Bulgarian foreign minister Daniel Mitov of centre-right GERB party in Sofia, Bulgaria, April 20, 2021. REUTERS/Stoyan Nenov

Bulgarian President Rumen Radev gives a mandate to form a new government to former Bulgarian foreign minister Daniel Mitov of centre-right GERB party in Sofia, Bulgaria, April 20, 2021. REUTERS/Stoyan Nenov

Bulgarian President Rumen Radev takes off his mask before delivering his speech at the first plenary session of the new parliament in Sofia, Bulgaria, April 15, 2021. REUTERS/Stoyan Nenov

A Bulgarian Muslim man carries his son on a horse as they attend a ritual ahead of a mass circumcision ceremony in the village of Ribnovo, Bulgaria, April 11, 2021. REUTERS/Stoyan Nenov

A Bulgarian Muslim man carries his son on a horse as they attend a ritual ahead of a mass circumcision ceremony in the village of Ribnovo, Bulgaria, April 11, 2021. REUTERS/Stoyan Nenov

A Bulgarian Muslim man leads his horse as he attends a ritual ahead of a mass circumcision ceremony in the village of Ribnovo, Bulgaria, April 11, 2021. REUTERS/Stoyan Nenov

Bulgarian Muslim oil wrestlers attend a ritual ahead of a mass circumcision ceremony in the village of Ribnovo, Bulgaria, April 11, 2021. REUTERS/Stoyan Nenov TPX IMAGES OF THE DAY

A Bulgarian Muslim man carries his son on a horse as they attend a ritual ahead of a mass circumcision ceremony in the village of Ribnovo, Bulgaria, April 11, 2021. REUTERS/Stoyan Nenov

Kornelia Ninova, Bulgarian Socialist Party leader, votes in a polling station during the parliamentary election in Sofia, Bulgaria, April 4, 2021. REUTERS/Spasiyana Sergieva

Kornelia Ninova, Bulgarian Socialist Party leader, votes in a polling station during the parliamentary election in Sofia, Bulgaria, April 4, 2021. REUTERS/Spasiyana Sergieva

Kornelia Ninova, Bulgarian Socialist Party leader, leaves after voting in a polling station during the parliamentary election in Sofia, Bulgaria, April 4, 2021. REUTERS/Spasiyana Sergieva

Kornelia Ninova, Bulgarian Socialist Party leader, speaks to the media after voting in a polling station during the parliamentary election in Sofia, Bulgaria, April 4, 2021. REUTERS/Spasiyana Sergieva

Kornelia Ninova, Bulgarian Socialist Party leader, votes in a polling station during the parliamentary election in Sofia, Bulgaria, April 4, 2021. REUTERS/Spasiyana Sergieva

Kornelia Ninova, Bulgarian Socialist Party leader, votes in a polling station during the parliamentary election in Sofia, Bulgaria, April 4, 2021. REUTERS/Spasiyana Sergieva

A man walks past a billboard with an election poster of the Bulgarian Socialist Party leader Kornelia Ninova in Sofia, Bulgaria, March 31, 2021. Picture taken March 31, 2021. REUTERS/Spasiyana Sergieva