Escalating violence in Syria has killed one Syrian every 25 minutes in the past 48 hours as the ceasefire stands on the brink of collapse, the United Nations Special Envoy on Syria said.

Staffan de Mistura added in the past two days one Syrian has been wounded every 13 minutes.

He said a political solution to the civil war is necessary as the ceasefire is "in great danger".

De Mistura said the ceasefire "is still there, but is in great danger, it is still alive but barely. The perception is that it could collapse at any time".

When asked about the role of President Assad in the talks, he said: "We didn't get into names or people, who is doing what, but about how to change the current governance."

De Mistura has held talks with the Syrian government delegation on Tuesday and Wednesday this week to discuss the raging civil war gripping the country.

He said the talks will only be meaningful when the "level of cessation of hostilities is brought back to the levels seen in February and March".

The ceasefire is in danger of collapsing in Aleppo and three other areas, he added.