Nobody was reported killed by fighting in Syria on Wednesday, the first day without casualties in three years, after a fierce winter storm quelled violence, a group that monitors the war said on Thursday.

Freezing temperatures brought new hardship for refugees and civilians but "the cold protected the Syrians from bombardment and fighting," said the head of the Syrian Observatory for Human Rights, Rami Abdulrahman.

An average of 150 people died every day through December in a conflict that has killed around 207,000 people since it erupted in 2011, according to Observatory figures.

But the UK-based organisation, which uses sources across Syria to track the conflict, did not register any deaths on any side as a result of fighting on Wednesday, Abdulrahman said.

One Islamist fighter died in Darraya near Damascus as a result of wounds sustained earlier, he added.

Blizzards, rain and strong winds have buffeted the Middle East this week, raising concerns for refugees who are facing the winter in flimsy shelters.