The Syrian government and opposition forces began a coordinated population swap on Friday of about 10,000 people from four towns besieged for years amid the country’s bloody, six-year civil war.

About 5,000 people were evacuated on 75 buses from two pro-government towns in northern Syria to the nearby city of Aleppo, said Abdul Hakim Baghdadi, who helped negotiate the arrangement.

The predominantly Shiite Foua and Kfraya have remained loyal to the Syrian government while the surrounding Idlib province has come under hard-line Sunni, rebel rule.

Near the capital of Damascus, some 60 buses carrying 2,350 opposition fighters, activists and their families departed from two opposition-held towns in the direction of Idlib, according to the Britain-based Syrian Observatory for Human Rights monitoring group and Syrian state media.

“We’ve moved. We’re at the outskirts of the towns,” said Muhammad Darwish, who provides medical care in the besieged town of Madaya. He was forced to leave the university in the final year of his dentistry studies when he joined the popular movement to unseat President Bashar Assad six years ago. The country has since descended into a harsh civil war.

If the evacuations are completed, they would be the first in number of rounds stretching over two months to evacuate some 30,000 Syrians from besieged areas.

According to an arrangement struck between rebels and the government and brokered by Qatar and Iran evacuations will also take place from the rebel-held town of Zabadani, which neighbors Madaya.

Critics have denounced the deal as forced displacement, and the U.N. is not supervising the evacuations. The Syrian Red Crescent is.

But residents in Zabadani and Madaya said conditions in their two towns had become too difficult to bear. They have been under siege by pro-government forces since summer 2015, leading residents to hunt rodents and boil grass to stave off hunger in the winter months. Photos of children gaunt from hunger shocked the world and gave new urgency to U.N. relief operations in Syria.