MOSCOW (Reuters) - Russia said its war planes had joined forces with Turkish jets for the first time on Wednesday to target Islamic State militants holding the town of al-Bab in northern Syria, evidence of increasingly close cooperation between Moscow and Ankara.

Chief of the Main Operational Directorate of the General Staff of the Russian Armed Forces Lieutenant General Sergei Rudskoy attends a news briefing in Moscow, Russia, October 17, 2016. REUTERS/Maxim Zmeyev

Russia and Turkey are the main organizers of a new round of Syrian peace talks due to take place in Kazakhstan on Jan. 23 and have set aside their differences over the political fate of President Bashar al-Assad to try to forge a wider Syria deal.

Moscow backs Assad, while Ankara has diluted its demands for the Syrian leader to urgently step down as part of what some sources say is a backroom deal aimed at dividing Syria into informal zones of regional power influence.

Lieutenant-General Sergei Rudskoi, a senior Russian Defence Ministry official, said that nine Russian jets and eight Turkish war planes had together struck targets in al-Bab, which is located around 40 km (25 miles) northeast of Aleppo.

“Today the Russian and Turkish air forces are conducting their first joint air operation to strike Islamic State in the suburbs of al-Bab,” Rudskoi said.

“The assessment of the initial results ... showed the strikes were highly effective.”

Turkish President Tayyip Erdogan wants Turkish-backed rebels to capture al-Bab to prevent Kurdish militias from doing so. Rudskoi said the joint mission had been conducted in agreement with the Syrian government.

He said the Russian air force was also providing air support to Syrian government troops trying to fight off an Islamic State assault around the town of Deir al-Zor.

The town’s civilian population could be massacred if Islamic State took Deir al-Zor, he said.

Russian jets were also backing a Syrian army offensive near the town of Palmyra, said Rudskoi, who added that Islamic State militants were planning to blow up more of the ancient city’s historical monuments.

“We have received information, confirmed by several sources, that a large amount of explosives has been brought into the Palmyra area and that the terrorists plan on destroying the city’s world-class historical legacy,” he said.

Significant numbers of Islamic State militants fleeing the U.S.-led coalition offensive against Mosul in neighboring Iraq were streaming into Syria “almost unobstructed,” Rudskoi said.