Kofi Annan, the joint UN-Arab League envoy to Syria, has released the following statement about developments in Aleppo. He has called for both sides in the conflict to respect international humanitarian and human rights law, echoing earlier comments from Navi Pillay, the UN's human rights chief.

I am concerned about reports of the concentration of troops and heavy weapons around Aleppo, in anticipation of an imminent battle in Syria’s largest city.

I remind the parties to the conflict of their obligations under international humanitarian law and human rights law, and urge them to exercise restraint and avoid any further bloodshed.

I believe that the escalation of the military build-up in Aleppo and the surrounding area is further evidence of the need for the international community to come together to persuade the parties that only a political transition, leading to a political settlement will resolve this crisis and bring peace to the Syrian people.