The leader of Syria’s most powerful insurgent group has toured the seized city of Aleppo in a surprise visit, for the first time since the group captured large parts of the city last weekend, as fierce fighting intensifies in the government-led counter-offensive in northern Hama.

The leader of Syria's most powerful opposition group toured the seized city of Aleppo on Wednesday in a surprise visit — the first since the group captured large parts of the city over the weekend as fierce fighting intensifies in the government-led counter-offensive in northern Hama.

Syrian and Russian jets are stepping up strikes on opposition forces in northern Syria in retaliation for the sudden offensive that has cost the regime control of the country’s second largest city, Aleppo.