Syrian rebels and their families were being evacuated from the besieged Eastern Ghouta enclave on Thursday as part of a deal brokered by Russia. Buses carrying rebel fighters and their families began to leave the town of Harasta. The 30 or so buses were carrying around 1,500 people, some 400 of whom were rebel fighters, a military source told Reuters. A Reuters camera team saw more empty buses lined up for another batch to leave on another day. The agreement, announced on Wednesday and brokered by Syrian regime ally Russia, could empty one of three rebel-held pockets in the region and mark a major advance in regime efforts to secure the nearby capital. It could also increase pressure on rebels to follow suit in the two other opposition-held pockets of the besieged enclave, where tens of thousands of civilians remain trapped under relentless bombardment. State television said 410 fighters were among hundreds of people who had boarded buses from Harasta, until now held by the Ahrar al-Sham rebel group. A military source told AFP the rebels and accompanying civilians had boarded buses and were in a buffer zone, waiting to cross into regime-controlled territory. Women and children walked nearby or sat by the side of the road waiting for the green light for the convoy to set off. Another military source said around 2,000 people are expected to leave in total, including around 700 fighters on Thursday. The evacuation has not however led to a let up in the bombardment of Eastern Ghouta. The Syrian Observatory for Human Rights said that 20 civilians were killed on early Thursday in renewed air strikes. Some 50,000 people have reached shelters in regime-controlled territory in the past week, according to the United Nations. On Wednesday, the UNs humanitarian coordinator in Syria said those displaced were living in "tragic" conditions. "People may have escaped fighting, fear and insecurity but they find themselves in a place without anywhere to wash themselves," Ali al-Zaatari said. The international medical charity Doctors Without Borders said the advancing regime forces had captured or destroyed 19 of the 20 hospitals the group was supporting just one week ago. It said medical staff were fleeing the approaching front lines. Since February 18, a devastating Russian-backed offensive on Eastern Ghouta has sliced the shrinking enclave into three isolated pockets. The regimes offensive on Ghouta has killed more than 1,500 civilians since February 18, according to Observatory. Meanwhile, in the northwestern province of Idlib, air strikes -- likely Russian -- killed 22 civilians in Harem, an area controlled by Hayat Tahrir al-Sham, the Observatory said. The deadly raid came a day after an air raid near a school in the town of Kfar Batikh killed 20 civilians, including 16 children.