A Ukrainian serviceman checks an area as he stands on the roof in Avdeyevka near Donetsk September 8, 2014. Ukrainian President Petro Poroshenko visited the eastern port of Mariupol on Monday and promised to deal a 'crushing defeat' to pro-Russian rebels massed on the edge of town if they tried to advance in violation of a ceasefire agreement. REUTERS/Gleb Garanich (UKRAINE - Tags: POLITICS CIVIL UNREST MILITARY)