The death toll in Syria's conflict has risen to at least 125,835, more than a third of them civilians, but the real figure is probably much higher, the Syrian Observatory for Human Rights said on Monday.
The pro-opposition monitoring group also appealed to U.N. Secretary General Ban Ki-moon and "all people in the international community who have a conscience" to increase their efforts to end the 2-1/2 year war.
The Observatory, based in Britain but with a network of activists across Syria, put the number of children killed in the conflict so far at 6,627.
It put the death toll among rebels fighting the Assad government at at least 27,746 rebels, including more than 6,000 categorized as foreign fighters or unknown combatants.
"The number is likely much higher but in many battles, the number of rebels killed is hidden, especially by the (al Qaeda-linked) Nusra Front and Islamic State of Iraq and the Levant," Rami Abdulrahman, head of the Observatory, told Reuters.
He said the observatory had documented 50,430 deaths among the Syrian armed forces and local militias supporting Assad, but said that number too was probably higher.
"There are at least 40,000 more dead combatants but they were not included in the toll because the cases were not documented well enough," Abdelrahman said.
"The Observatory calls for … serious efforts (by the international community) to stop the killing in Syria and help its people transition to a democratic state with freedom, justice and equality," it said in a statement.
The U.N. does not give regular casualty counts for Syria. It has said for months that more than 100,000 have died.