Officials from Russia, Iran and Turkey assembled with representatives of the Syrian opposition and the Syrian regime in the Kazakh capital Astana today. The first order of business was reportedly to ensure that a shaky cease-fire in the rebel-held province of Idlib agreed in September doesn’t collapse.

Worries that the violence would escalate grew after Russian war planes struck opposition targets in Hama and Idlib provinces Sunday. It was the sharpest flare-up since mid-September, when Turkey and Russia sealed an agreement designating a demilitarized zone encircling Idlib and parts of rebel-held Aleppo and Hama provinces. The Russians said they were responding to an alleged chemical attack on Aleppo city’s al-Khalidiya neighborhood by opposition rebels the same day.

The talks, the 11th round in the Astana peace process, kicked off as Turkey’s President Recep Tayyip Erdogan spoke over the telephone with his Russian counterpart Vladimir Putin to discuss recent tensions between close Turkish ally Ukraine and Russia over control of the Azov Sea. But the issue of Idlib, where Turkey is tasked — impossibly, many analysts say — with clearing out the al-Qaeda-linked Hayat Tahrir al-Sham and co-opting “moderates,” may well have also been been broached. Erdogan had a separate call with US President Donald Trump to relay his conversations with Putin and Ukrainian President Petro Poroshenko, Turkey’s state-run Anadolu news agency reported.

The Organization for the Prohibition of Chemical Weapons, a watchdog group that has investigated allegations of chemical weapons use during the seven-year Syrian conflict, said it was investigating government claims that hard-line Islamists used chlorine gas against civilians.