Members of the US-backed Syrian Democratic Forces (SDF) at the Taqba Dam on March 28, 2017
Four Syrian towns are to be evacuated under an agreement between pro-government forces and rebels, in the latest of a series of deals to end crippling years-long sieges.
The agreement, brokered by rebel supporter Qatar and regime ally Iran, is expected to involve more than 30,000 people, said the Syrian Observatory for Human Rights.
The deal reached late Tuesday involves Zabadani and Madaya, besieged by regime fighters near Damascus, and Shiite-majority Fuaa and Kafraya in northwest Syria that are encircled by rebels.
Such evacuations have been touted by President Bashar al-Assad as a way to end his country's six-year war, but his opponents say the regime is redrawing Syria's map with forced displacement.
The conflict has killed more than 320,000 people and forced millions more from their homes.
In the central city of Homs, where evacuations from the last rebel-held district resumed last month, a bomb on a bus killing five people on Wednesday, state media said.
The Observatory, a British-based monitor, said the residents of Zabadani, Madaya, Fuaa, and Kafraya are to quit their hometowns over the course of 60 days from next Tuesday.
All of the residents of Fuaa and Kafraya are expected to leave, while it was unclear if the evacuations of Madaya and Zabadani would empty the towns completely.
Part of the Yarmuk Palestinian camp south of Damascus is also to be evacuated.
- Truce takes effect -
"As a goodwill measure, a ceasefire for the towns came into effect overnight," said Observatory chief Rami Abdel Rahman, adding it would last nine months.
In all, 32,000 people are expected to be evacuated, he told AFP.
Hassan Sharaf, who is coordinating the deal for the government, said a total of 16,000 people would quit Fuaa and Kafraya "in two waves" going first to Aleppo, then on to Latakia and Damascus.
At least 600,000 people are living under siege in Syria, according to the United Nations, with another four million people in so-called "hard-to-reach" areas.
The four towns are part of an existing deal reached in 2015 that has seen simultaneous evacuations and aid deliveries, the last of which took place in November.
The new deal, which Syria's Arab Red Crescent will help implement, also stipulates that Syria's government release 1,500 prisoners held for political activism since the uprising began in 2011 but gives no time frame.
In Damascus on Wednesday meanwhile, Assad replaced the justice, economy, and development ministers, without giving a reason.
- Turkey ends Syria campaign -
The UN has hosted several rounds of peace talks in Geneva to try to reach a political solution to the conflict.
On Wednesday, UN envoy Staffan de Mistura met with opposition delegates and government representatives.
And Russia's deputy foreign minister Genady Gatilov held talks with opposition delegates, after meeting government representatives on Monday.
Expectations for the talks remain limited, with the two sides still far apart on resolving a conflict that began with anti-government protests but has become a complex war putting government forces, rebels, Kurds, and jihadists against each other.
Turkey, which sent troops into northern Syria in August, announced Wednesday its military campaign in the war-torn country has been "concluded successfully". It did not specify whether it would pull them out.
US-backed fighters are waging an offensive in northern Syria to encircle the Islamic State group's Syrian bastion of Raqa.
The campaign is now focused on the key IS-held town of Tabqa and the adjacent dam on the Euphrates River, where engineers carried out urgent maintenance on Wednesday.
The technicians came under fire from at least six IS shells as they worked to open a spillway to drain water that had built up in the reservoir, AFP's correspondent there said.
People could be seen running for cover along part of the dam, whose northern entrance has been captured by the US-backed Syrian Democratic Forces.
But the engineers were able to complete their work and leave, an SDF official and the Observatory said.
"Water has begun to flow out. The technicians were able to open the door and ease pressure on the dam," the official said.
The UN has warned of catastrophic flooding downstream if the dam were to burst, but the SDF and the US-led coalition have insisted there is no structural damage.
Technicians inside the complex and the Observatory said the dam's main electrical control room had been knocked out.
SDF fighters have advanced to within eight kilometres (five miles) of Raqa city at their closest point.
Government forces meanwhile advanced against IS further west in Aleppo province, taking the village of Deir Hafer and securing 24 kilometres of the Aleppo-Raqa highway, state media said.