The evacuation of more than 3,000 Syrians that was scheduled to take place on Sunday as part of a population transfer has been postponed, a day after a deadly blast killed more than 120 people.
The United Nations is not overseeing the transfer deal, which involves residents of the pro-government villages of Foua and Kfarya and the opposition-held towns of Madaya and Zabadani.
All four areas have been under siege for years, their fate linked through a series of reciprocal agreements that the UN says have hindered aid deliveries.
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Rami Abdurrahman, who heads the Britain-based Syrian Observatory for Human Rights, and Hezbollah's Al-Manar TV, earlier said that 3,000 people will be evacuated from Foua and Kfarya.
Another 200, the vast majority of them fighters, will be evacuated from Zabadani and Madaya.
But Abdurrahman and opposition activist Hussam Mahmoud, who is from Madaya, said the evacuation has since been delayed.
Abdurrahman said no permission was given for the evacuation to go ahead while Mahmoud said it has been delayed for "logistical reasons".
It was not immediately clear if the evacuees feared attacks similar to Saturday's bombing.
Abdurrahman said Saturday's blast -which hit an area where thousands of pro-government evacuees had been waiting for hours - killed 126.
He said the dead included 109 people from Foua and Kfarya, among them 80 children and 13 women.
Nobody has claimed responsibility for the attack, but both the Islamic State group and the al-Qaeda-affiliated Fatah al-Sham Front have targeted civilians in government areas in the past.
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The delay comes as shells fired by the Islamic State group on government-held parts of the eastern city of Deir el-Zour wounded two members of a Russian media delegation visiting the area, according to state-run Syrian news agency SANA.
Russia is a main backer of Syrian President Bashar Assad and Russian journalists enjoy wide access in government-held parts of the country.
Russia's Anna-News military news service, which employs the journalists, said one was wounded in the arm while the other suffered leg and stomach wounds.
The news service said the two were evacuated adding that their condition was "satisfactory."
