Children evacuees, from the besieged rebel-held Syrian town of Zabadani gesture from inside a bus upon their arrival at an exchange point supervised by the Syrian Arab Red Crescent, in the town of Qalaat al-Madiq, in Hama province, Syria, on April 21, 2016.

Four Syrian towns that have been under crippling siege for more than two years are to be evacuated under a deal reached late on Tuesday, a monitoring group said.

Residents of Zabadani and Madaya, two towns near Damascus under siege by government forces, will leave their homes in return for the evacuation of Fuaa and Kafraya, two mainly Shiite towns in the northwest besieged by the rebels, the Syrian Observatory for Human Rights said.

Observatory chief Rami Abdel Rahman said the deal was brokered by rebel supporter Qatar and government ally Iran and that Islamist rebels in the northwestern province of Idlib had already signed on.

“The evacuations are not expected to begin until April 4 but, as a goodwill measure, a ceasefire for the towns came into effect overnight,” Abdel Rahman said.

“It is calm there now,” he added.

Existing deal

The four towns are part of an existing deal reached in 2015 that has seen aid deliveries and evacuations.

Relief convoys to the four towns are always simultaneous and equal, with the same number of trucks entering at the same time. A similar stipulation has applied for those being evacuated.

More than 320,000 people have been killed and millions more displaced since the Syrian conflict erupted with protests against President Bashar al-Assad in March 2011.

Multiple attempts to secure a nationwide ceasefire have faltered.

In December, rebel backer Turkey and government ally Russia brokered a cessation of hostilities that aimed to pave the way for more aid deliveries and peace talks, but fighting has continued across swathes of the country.