(VOVworld) – The Vienna talks of the International Syria Support Group (ISSG) on ending the Syrian conflict closed with no clear breakthrough while faction-fighting erupted and the death toll continued to increase.

Russian Foreign Minister Sergei Lavrov speaks to US Secretary of State John Kerry ahead a joint press conference in Vienna, Austria, on May 17, 2016 (Photo by: AFP)

US Secretary of State John Kerry and Russian Minister of Foreign Affairs Sergei Lavrov said the Syria contact group they co-chair agreed to bolster a shaky ceasefire. But, disagreements between Washington and Moscow on how to handle the crisis were apparent, and the United Nations failed to name a date for new peace talks.

Meanwhile, human rights monitors says fierce new clashes between the rebel Jaish al-Islam and Al-Qaeda-backed factions had left 50 fighters and two civilians dead.

United Nations Syria envoy Staffan de Mistura says he can not invite Bashar al-Assad's regime and the Syrian opposition back to peace talks without a credible ceasefire.