Iraqi forces preparing advance on south Mosul as they work to drive out Isis

Separately, human rights group accuse men dressed as Iraqi police officers of killing villagers around Mosul

Troops in the US-led coalition make progress towards Mosul airport on Sunday (AP)

Iraqi security forces are preparing to advance towards Mosul airport on the city's southern edge to increase pressure on Isis fighters battling troops who breached their eastern defences.

The rapid response forces, part of a coalition seeking to crush the jihadis in the largest city under their control in Iraq or Syria, took the town of Hammam al-Alil, just over 10 miles south of Mosul, on Monday.

Officers say they plan to resume their advance north, up the western bank of the Tigris River towards the city of 1.5 million people who have lived under the ultra-hardline Sunni Islamists for more than two years.

More than three weeks after the US-backed campaign to retake Mosul was launched, the city is almost surrounded by the coalition of nearly 100,000 fighters. But troops have entered only a handful of neighbourhoods in the east of the city.

“We need to put wider pressure on the enemy in different areas,” said Major-General Thamer al-Husseini, commander of the elite police unit which is run by the Shia-controlled Interior Ministry.

He said operations would resume within two days.

Lieutenant-Colonel Dhiya Mizhir said the target was an area overlooking Mosul airport, which has been rendered unusable by Isis to prevent attackers using it as a staging post for their offensive.

Satellite pictures released by intelligence firm Stratfor also showed Isis had dug deep trenches in the runways and destroyed buildings to ensure clear lines of sight for defenders and to prevent advancing forces from using hangars or other facilities.

Separate forces advancing on the eastern side of the Tigris targeted two villages on Thursday on the edge of the ancient Assyrian city of Nimrud, a military statement said.

Troops from the Ninth Armoured Division took the village of Abbas Rajab, around two miles east of Nimrud, and raised the Iraqi flag.

The Iraqi government says Nimrud was bulldozed last year as part of Isis's campaign to destroy symbols which they consider idolatrous. It would be the first such site to be recaptured from Isis.

Counter-terrorism forces and an armoured division fighting in the east of the city have been battling to hold on to half a dozen districts they surged into a week ago.

They have been hit by waves of attacks by Isis units, including snipers, suicide bombers, assault fighters and mortar teams, who have used a network of tunnels under the city and civilian cover in the narrow streets to wear them down in urban warfare.

Also on Thursday, men dressed as Iraqi federal police forces were accused of killing and torturing civilians by human rights group Amnesty International, in the first such reports of alleged abuse in a US-backed campaign to retake the city.

Amnesty said up to six people were found dead last month in the Shura and Qayyara sub-districts.

“Men in federal police uniform have carried out multiple unlawful killings, apprehending and then deliberately killing in cold blood residents in villages south of Mosul,” said Lynn Maalouf, deputy director for research at Amnesty's Beirut office.

Iraqi Prime Minister Haider al-Abadi denied the Amnesty report, saying local residents, not government forces, had killed Isis members. He also said the rights group was spreading fear among Iraqis with its reports and would bear responsibility for displacement of people who might flee the city as a result.

Human Rights Watch (HRW) said at least 37 men suspected of being affiliated with Isis had been detained by Iraqi and Kurdish forces from checkpoints, villages, screening centres and camps for displaced people around Mosul and Hawija, further south.

Relatives said they did not know where most of the men were being held and had not been able to contact any of them while in detention, according to the report.

HRW said such conduct “significantly increases the risk of other violations”, including torture.

An Interior Ministry spokesman denied there had been any violations and said Iraqi forces respected human rights and international law.

A spokesman for the Kurdish regional government denied the HRW report, saying any delays in informing families were limited due to a shortage of resources. “Nobody has been kept in unknown facilities. They are kept in identified facilities,” said Dindar Zebari.

Reuters