Russian and Turkish war planes joined forces to bomb Islamic State (IS) militant targets in a suburb of war-ravaged Aleppo.

Russian Lieutenant-General Sergei Rudskoi said Wednesday that the bombing of al-Bab, a town about 40 kilometers (25 miles) northeast of Aleppo, marked the first time the two country's air forces had teamed up in such a manner.

Rudskoi, a senior Russian Defense Ministry official, said on television that the Syrian government agreed to the joint assault.

The general said the Russian air force was also supporting Syrian government ground-troops trying to defend against an IS attack on the town of Deir el-Zour.

Russian jets were also providing air-cover for a Syrian army attack near Palmyra. He warned that IS militants may be planning to blow up more of the ancient city's historical monuments, though he did not elaborate.

Meanwhile, in Geneva, the new UN Secretary General warned that Syria's civil war has caused global threats that have become "too dangerous" to leave unresolved. The message was aimed at creating a need for progress at peace talks due to convene next week.

Antonio Guterres said the conflict had heightened instability across the Middle East and promoted terrorist attacks around the world.

"The consequences of this conflict have become too dangerous for everyone," said Guterres, speaking to reporters at the United Nations in Geneva.

Peace talks in Kazakhstan

Peace talks among some of the warring factions are scheduled to open Monday in Astana - the capital of Kazakhstan. The talks are being convened under the auspices of Syria's chief patron - Russia - and Syria's regional rival - Turkey.  The United Nations and the United States are conspicuously absent from the talks.

Still, Guterres expressed hope that the negotiations "can lead towards a consolidation of the ceasefire and a freeze in the conflict."

Progress in Astana "can help create the conditions for a political process that should resume in Geneva in February that can lead to concrete results," he added.

The UN's Geneva peace process is being led by Guterres's Syria envoy Staffan de Mistura, who is aiming to restart talks on February 8. De Mistura has been invited to Astana, but is sending deputies to represent the UN.

Guterres, who became secretary general on January 1, was making his second trip to Geneva as the UN leader.

He previously worked for a decade as the head of the UN's refugee agency before being named to the body's top job.

He was due to receive Chinese President Xi Jinping later Wednesday.

bik/rc (Reuters, AFP)