Islamic State militants killed 40 former members of the Iraqi Security Forces near Mosul on Saturday and threw their bodies in the Tigris river, UN human rights spokeswoman Ravina Shamdasani said today, citing reports from the field.

IS also tried to transport about 25,000 civilians from Hammam al-Alil, a town south of Mosul, on trucks and minibuses during the hours of darkness early on Monday, probably for use as human shields in defence of IS positions, she said.

Most of the trucks turned back under pressure from patrolling aircraft, but some buses did reach Abusaif, 15 km north of Hammam al-Alil, she said.

Iraqi forces backed by a US-led air coalition targeted Islamic State defences on the eastern edge of Mosul with artillery fire and air strikes today, a day after fighting for the first time inside the city.

Mosul is many times bigger than any other city controlled by Islamic State in either Iraq or Syria. Its recapture would mark the end of the Iraqi wing of the caliphate which it declared in parts of both countries two years ago although the hardline Sunni militants have recovered from previous setbacks in Iraq.