BEIRUT: More than 136,000 people have been killed since the beginning of the Syrian conflict in March 2011, with January one of the bloodiest months on record, an NGO said Saturday.

The Syrian Observatory for Human Rights, a monitoring group based in Britain, said the toll was now at least 136,227 people killed.

Among those are 47,998 civilians, including more than 7,300 children, the group said.

“January was among the bloodiest months since the beginning of the conflict,” Observatory director Rami Abdel Rahman said.

“We in the Syrian Observatory for Human Rights will continue to call on all actors on the international stage to do their humanitarian and moral duty to press for the Syrian file to be referred to the International Criminal Court,” the group said in a statement.

The group said it sought “the trial of the murderers of the Syrian people, and those who have collaborated with them”.

The Observatory's last toll, at the end of December, stood at 130,433, but fierce fighting between rebels and the regime, as well as between rebels and jihadists, has claimed nearly 6,000 lives since then.

The group said at least 31,629 opposition fighters, including more than 8,000 jihadists, had been killed since the start of the conflict.

On the regime side, 53,167 soldiers and militiamen were killed, along with 271 members of Lebanon's Shiite movement Hezbollah and 338 members of other foreign Shiite brigades fighting alongside the government.

The toll also includes 2,824 unidentified individuals whose deaths the Observatory has documented.

The group said the real toll could be much higher than recorded so far, citing “extreme secrecy” by rebels, jihadists and regime troops about the number of their dead.

Syria's bloody conflict began in March 2011, with peaceful anti-government demonstrations.

The regime of President Bashar al-Assad cracked down hard on the protests, and the opposition took up arms.

The conflict has spiralled into an increasingly bloody civil war, with human rights groups accusing both sides of suspected war crimes.