With its already searingly hot summers, Iraq is among the most vulnerable countries to climate change and Saleh had been due to address the summit on Tuesday.

But the Kurdish politician, whose office is largely ceremonial, decided to cancel "at the last minute in light of security developments in Diyala and Kirkuk, and the political crisis linked to the recent parliamentary election," the aide said, speaking on condition of anonymity.

An attack claimed by the Sunni extremist Islamic State group on a mainly Shiite village in ethnically and confessionally mixed Diyala province killed 15 civilians last week.

In reprisal, villagers attacked a neighbouring Sunni village, killing 11 people.

In Kirkuk province further north, two Kurdish peshmerga fighters were killed in another attack claimed by IS on Saturday evening.

Iraq is bracing for the official results of its October 10 general election which are expected to see losses for the staunchly pro-Iranian political arm of the Hashed al-Shaabi paramilitary alliance.

Several hundred of its supporters have been camped outside Baghdad's Green Zone government and diplomatic district protesting against alleged electoral fraud.

Ahead of the UN summit, Saleh had spoken out in favour of tough goals to limit climate change, penning an opinion piece in Monday's edition of the Financial Times in which he said they should be a national priority.