Israelis take cover as a siren warning of incoming rockets sounds in the Israeli-occupied Golan Heights, near the ceasefire line between Israel and Syria June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner

Smoke rises during fighting in the village of Ahmadiyah in Syria, as seen from the Israeli side of the border fence between Syria and the Israeli-occupied Golan Heights, June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner TPX IMAGES OF THE DAY

Israeli soldiers ride armoured vehicles during an exercise in the Israeli-occupied Golan Heights, near the ceasefire line between Israel and Syria June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner 

Members of the Druze community hold a picture depicting a meeting with Syrian President Bashar al-Assad, during a protest in the Druze village of Majdal Shams on the Golan Heights, June 15, 2015. Several hundred members of the Druze community on Monday called on Syrian President Bashar al-Assad to protect their Syrian kin following last week's killing of 20 Druze villagers by the Nusra Front, Syria's al Qaeda branch, during fighting in the ongoing Syrian civil war. Israel captured the Golan Heights from Syria in the 1967 Middle East war and annexed the territory in 1981, a move not recognised internationally. REUTERS/Ammar Awad

Members of the Druze community watch the fighting in the Druze village of Khadr in Syria, as they stand on the Israeli side of the border fence between Syria and the Israeli-occupied Golan Heights, near Majdal Shams, June 16, 2015. Israel's president expressed his concern to the United States last week about the fate of the Druze minority in Syria, saying around 500,000 of them were under threat from Islamist militants in an area near the Israeli border. REUTERS/Baz Ratner

A placard depicting Syrian President Bashar al-Assad is waved along with Syrian flags during a protest in the Druze village of Majdal Shams on the Golan Heights, June 15, 2015. Several hundred members of the Druze community on Monday called on Syrian President Bashar al-Assad to protect their Syrian kin following last week's killing of 20 Druze villagers by the Nusra Front, Syria's al Qaeda branch, during fighting in the ongoing Syrian civil war. Israel captured the Golan Heights from Syria in the 1967 Middle East war and annexed the territory in 1981, a move not recognised internationally. REUTERS/Ammar Awad

An Israeli soldier sits atop a tank during an exercise in the Israeli-occupied Golan Heights, near the ceasefire line between Israel and Syria June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner

Smoke rises during fighting in the Druze village of Khadr in Syria, as seen from the Israeli side of the border fence between Syria and the Israeli-occupied Golan Heights, near Majdal Shams, June 16, 2015. Israel's president expressed his concern to the United States last week about the fate of the Druze minority in Syria, saying around 500,000 of them were under threat from Islamist militants in an area near the Israeli border. REUTERS/Baz Ratner

Members of the Druze community use binoculars to watch the fighting in the Druze village of Khadr in Syria, as they stand on the Israeli side of the border fence between Syria and the Israeli-occupied Golan Heights, near Majdal Shams, June 16, 2015. Israel's president expressed his concern to the United States last week about the fate of the Druze minority in Syria, saying around 500,000 of them were under threat from Islamist militants in an area near the Israeli border. REUTERS/Baz Ratner

An Israeli soldier adjusts sights on a tank in the Israeli-occupied Golan Heights, near the ceasefire line between Israel and Syria, June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner 

Israeli army armoured vehicles are seen during an exercise in the Israeli-occupied Golan Heights, near the ceasefire line between Israel and Syria June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner 

Members of the Druze community hold flags, as they watch fighting in Syria's ongoing civil war, next to the border fence between Syria and the Israeli-occupied Golan Heights, near the Druze village of Majdal Shams, June 16, 2015. Israel's president expressed his concern to the United States last week about the fate of the Druze minority in Syria, saying around 500,000 of them were under threat from Islamist militants in an area near the Israeli border. REUTERS/Baz Ratner

Smoke rises during fighting in Syria, as seen from the Israeli side of the border fence between Syria and the Israeli-occupied Golan Heights, June 17, 2015. Israel signaled readiness on Tuesday to intervene if Syrian refugees were to throng to its armistice line on the Golan Heights, after Israel's Druze Arab minority stepped up a public campaign to help brethren caught up in the civil war next door. REUTERS/Baz Ratner

Members of the Druze community carry flags at they walk towards the border fence between Syria and the Israeli-occupied Golan Heights, near the Druze village of Majdal Shams, to watch the fighting in Syria's ongoing civil war June 16, 2015. Israel's president expressed his concern to the United States last week about the fate of the Druze minority in Syria, saying around 500,000 of them were under threat from Islamist militants in an area near the Israeli border. REUTERS/Baz Ratner