A new high-level meeting of the countries backing peace efforts in Syria is "urgently" needed, the UN top envoy for the war-ravaged country said Friday, as violence surged on the ground.

"We do need certainly a new ISSG at the ministerial level, because the level of danger ... (means such a meeting) is urgently required," Staffan de Mistura told reporters, referring to the 17-country International Syria Support Group co-chaired by Washington and Moscow.