The diplomat tasked with ending Syria's civil war said that the conflict is worsening on Thursday, the same day he travelled to the country for the first time since taking up a job he himself has called "nearly impossible".

Lakhdar Brahimi, the U.N.-Arab League envoy, was expected to meet Syrian President Bashar Assad on Friday. He also was to meet members of the Syrian opposition.

"We came to Syria to consult with our Syrian brothers," Brahimi said on arrival at the airport in Damascus. "There is a crisis in Syria and I believe it is getting worse."

Brahimi replaces Kofi Annan, who left the job in frustration in August after his efforts failed to stem a conflict that started in March 2011. Activists estimate some 23,000 people have been killed in the bloodshed.

The visit comes as violence convulses the country's largest city, Aleppo, and the outskirts of the capital, Damascus. Activists said regime forces shelled Aleppo and clashes with rebels were reported outside Damascus.