UN Syria envoy urges combatants to put down their guns

The UN's peace envoy to Syria warned Thursday of unacceptable levels of human suffering from the escalating violence in the country and urged all parties to put down their guns and return to negotiations.

Addressing the UN Security Council in New York, Geir Pedersen described air and ground strikes in the northwestern region of Idlib, the last remaining rebel bastion in Syria's chaotic civil war, forcing thousands more people to flee their homes.

"Heavy strikes from both air and ground are causing massive waves of civilian displacement and major loss of civilian life," Pedersen, a Norwegian diplomat, told the 15-nation body in midtown Manhattan.

"This is causing totally unacceptable human suffering — and endangering international peace and security. And yet it can — and therefore must — stop now."

Russian-backed Syrian forces advanced through Idlib province on Thursday in a brutal ground offensive that was preceded by weeks of intensive aerial bombardment which emptied whole towns of terrified civilians.

Tensions between Turkey and the government of Syrian President Bashar al-Assad escalated this week after Turkish and regime forces exchanged deadly fire in a rare face-off that left more than 20 people dead on the two sides.

"I appeal for an end to the hostilities. And I appeal to all for a serious international effort to cooperate on Idlib. It is a humanitarian imperative," said Pedersen.

"It is the way to have effective counter-terrorism. It is in the interests of regional and international peace and security. And it is an essential foundation for a sustainable path out of the Syrian conflict which is now approaching its tenth year."

At the same meeting, Britain's UN ambassador Karen Pierce warned that the "worst nightmare on Idlib has come to pass" as those displaced in previous phases of the civil war are once again forced to seek safety elsewhere.

"Turkey has made efforts to seek a peaceful solution in Idlib and to prevent millions more Syrians having to seek refuge. But we've seen the Syrian authorities frustrate and ignore the memoranda of understanding," said Pierce.

"Geir outlined the attacks that we've seen in the last few days that led to Turkish fatalities and increased the risk of a further regional conflagration. And we're deeply concerned at the impact of this escalation on Turkey, who are already hosting over three and a half million refugees who have fled the repression in Syria."

Syria's ongoing civil war has claimed some 380,000 lives and forced millions more from their homes since fighting erupted in 2011 with the repression of pro-democracy protests against Assad's leadership.