Turkish President Tayyip Erdogan and Saudi Arabia's King Salman spoke by phone late on Tuesday and said attacks by Russia and Syrian government forces north of Aleppo were worrisome, sources at Erdogan's office said.

Saying there could be no solution to the Syrian conflict with President Bashar al-Assad remaining in power, the two leaders called for an end to strikes on civilians and the lifting of sieges.

They said the attacks were making the humanitarian situation in the region worse.

Erdogan and King Salman also discussed attacks by Kurdish militia PYD on the northern Syrian town of Azaz, close to the Turkish border, and the shelling by the Turkish army in response.