Iraq's outgoing prime minster pledged Monday to turn his country into "a big grave" for Sunni militants from the Islamic State in Iraq and Syria (ISIS) group and commended security forces who achieved a rare victory over insurgents by ending the siege of a Shia town.

Nouri al-Maliki made the comments during an unannounced visit to the northern community of Amirli, where he was greeted with hugs. A day earlier, Iraqi forces backed by Iran-allied Shia militias and U.S. airstrikes broke a two-month siege of the town where some 15,000 Shia Turkmens had been stranded.

In footage aired on state TV, al-Maliki was shown sitting at a wooden desk in front of a large poster of Shia leader Grand Ayatollah Ali al-Sistsani, ordering promotions and awards for those who fought in the battle.

"I salute you for your steadfastness and patience against those beasts and killers," he told a gathering of fighters in a large hall as they chanted Shia religious slogans. He vowed to root out Sunni militants from areas they control in the country.

"All Iraq will be a grave for those infidels, and we will send all the [ISIS] gang to death," he added.

Humanitarian aid arrives

Hours before the visit, humanitarian aid began flowing to the town.

Four trucks loaded with food and medicine arrived after being sent by the Iraqi government and the Iraqi Red Crescent, according to Ali al-Bayati, who heads the aid organization called the Turkmen Saving Foundation. Soldiers began bringing food to families in their houses Sunday night.

A girl carries water bottles she received from a Kurdish political party after the siege by ISIS militants was broken in Amerli. (Youssef Boudlal/Reuters) "The situation is getting back to normal, but gradually," al-Bayati told The Associated Press. "Some people have come out from their houses and walked in the street. Shops are still closed, but people are happy to see their city secured by Iraqi security forces."

Shia Turkmen lawmaker Fawzi Akram al-Tarzi said the U.S. airstrikes and Iranian support for Iraqi forces "have played a positive role in defeating the terrorists," although he said the airstrikes "came late" in the battle.

On Monday, Iraqi security forces and Shia militiamen retook the nearby town of Suleiman Beg following fierce clashes with Sunni militants, Al-Tarzi said.

"The brave people of Amirli have made their town a new Stalingrad," he added, referring to the former name of the Russian city of Volgograd, famous for resisting a long siege by the German military during World War II. "Amirli people have clearly shown that Iraqis could not be intimidated by terrorists."

U.S. airstrikes helped liberate Amirli

Since early this year, Iraq has faced a growing Sunni insurgency led by an al-Qaeda-breakaway group, ISIS. With help from allied militants, they have taken over territory in the country's north and west and created Iraq's worst crisis since the 2011 withdrawal of U.S. troops.

Iraqi security forces and Shia militias advance toward the town of Amerli on Monday. Today, the UN approved a motion by Iraq to investigate alleged human rights crimes by ISIS. (Reuters) In June, a summer offensive stunned Iraqi security forces and the military, which melted away and withdrew as ISIS overran the northern cities of Mosul and Tikrit, as well as small towns and villages on their path.

Since then, Iraqi security forces and Shia militias have been fighting the militants without achieving significant progress on the ground.

Thousands of fighters from Iranian-backed Shia militias have answered a call by al-Sistani to join government forces in the fight.

The U.S. airstrikes that helped liberate Amirli were the first to hit areas where Iranian-backed militias were fighting Sunni militants, possibly outlining an unlikely alliance between the U.S. and Shia militiamen who once fought American soldiers in Iraq.

Military advisers from Iran's Revolutionary Guard have been guiding Shia militiamen in artillery attacks on Sunni positions.

Nearly 1,500 Iraqis killed in August

Since Aug. 8, the U.S. has carried out at least 120 airstrikes with aircraft and unmanned drones. The American military has focused on areas bordering the self-ruled northern Kurdish region where Kurdish forces have been fighting the militants.

Also Monday, the United Nations said that at least 1,420 Iraqis were reported killed in violence in August, down from the previous month.

The UN mission to Iraq, known as UNAMI, said in its monthly statement that the death toll includes 1,265 civilians and 155 members of Iraq's security forces. Another 1,370 were wounded, including 1,198 civilians.

July's death toll stood at 1,737 people. In June, 2,400 were killed as Sunni militants swept across the country, the highest figure since at least April 2005.

The statement said the figures are the "absolute minimum" number of casualties and do not include deaths in the western Anbar province or other parts of northern Iraq that have been held by militants for months. It added: "The actual figures could be significantly higher."