AlQa'dah 20, 1435, September 15, 2014, SPA -- Shelling killed six people and wounded 15 others in the rebel stronghold of Donetsk, the city council said Monday, the worst reported violence since a cease-fire between Russian-backed rebels and Ukrainian troops took effect on Sept. 5, AP reported. Nonetheless, the cease-fire deal has brought some normalcy to parts of eastern Ukraine and allowed prisoners on both sides to go home. Another 73 Ukrainian soldiers were freed Sunday night in an exchange with the rebels, Col. Andriy Lysenko, spokesman for the Ukrainian National Security and Defense Council, said Monday. Donetsk rebel leader Andrei Purgin was quoted by Interfax news agency as confirming that 73 rebels had been released in return. It was the largest reported prisoner exchange amid the fighting that began in mid-April. Fighting around Donetsk's government-held airport has left many northern neighborhoods in the crossfire. Over the weekend, Ukraine said its troops repelled an attack of 200 rebel fighters, but suffered no military casualties.