UN special envoy Staffan de Mistura said Wednesday that he hopes to convene a new round of Syria talks in Geneva in the coming weeks.

"I am calling on both sides to assess the situation with realism and responsibility to the people of Syria and to prepare seriously to participate in the Geneva talks," de Mistura said at the UN Security Council.

He said he intends to convene an eighth round of talks on the bloody more than six-year conflict no later than the end of October or early November.

De Mistura has already hosted seven rounds of largely unsuccessful talks in Geneva, with the fate of Syrian President Bashar al-Assad one of the main obstacles to progress.

Syrian opposition groups and various Western powers insist that Assad must go. But with his military position in the ascendant, he has little motivation to make concessions.

At the same time, there is a second process of negotiations in Kazakh capital Astana that has led to the establishment of multiple "de-escalation zones" that have contributed to a reduction in violence.

"These developments have had a positive impact on civilians," said Mark Lowcock, the UN's head of humanitarian affairs and emergency relief.

But "we continue to receive reports of violations of international humanitarian law by all parties to the conflict," he said.