The UN has stopped updating the death toll from Syria’s civil war.

It says it can no longer verify the sources of information that led to its last count of at least 100,000 people dead in late July last year.

Rupert Colville, a spokesman for the UN Office of the High Commissioner for Human Rights, said that the organisation lacked feet on the ground in the country and that it was unable to verify “source material” from those with access.

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“It was always a very difficult figure,” said Colville. “It was always very close to the edge in terms of how much we could guarantee the source material was accurate.”

He added: “It reached a point where we felt we could no longer cross that line. So for the time being, we're not updating those figures.”

Colville also said the UN could not endorse counts put forward by other bodies, including the widely quoted figures from the Syrian Observatory for Human Rights, whose latest tally is more than 130,000.

President Bashar al-Assad's forces and rebels have been fighting for nearly three-years.

On Tuesday, Damascus was hit by an airstrike that was reportedly caused by forces loyal to President Assad's regime.

Meanwhile, the head of an al-Qa'ida-linked rebel group in Syria called for a ceasefire between opposition forces who have clashed for five days in the most violent infighting since the civil war began.

The leader of the Nusra Front also said in a recording that the Islamic State in Iraq and the Levant group is to blame for the bloodshed.

It is not possible to verify the authenticity of the audio statement, but it was posted on a Twitter account used by the Nusra Front.

Additional reporting by Associated Press