AlQa'dah 12, 1435, September 07, 2014, SPA -- Strong explosions were heard early Sunday on the outskirts of the main rebel-held city in eastern Ukraine near the airport, raising new fears that a cease-fire signed two days ago is on the verge of collapse, AP reported. Blasts powerful enough to be heard in downtown Donetsk came from the area near the airport, which has been under the control of government troops since May and has come under unremitting attacks from pro-Russia separatist rebels since then. The cease-fire had appeared to be holding for much of the day on Saturday, but shelling started late at night. A rebel statement said Ukrainian forces violated the cease-fire by firing on their positions in six locations on Saturday, including near the Donetsk airport. The statement said several rebels were killed.