The Islamic State group strung up four Iraqi Shiite fighters with chains and burned them alive, according to footage posted online, the latest gruesome execution video from the jihadists.

The victims -- identified as fighters in the pro-government Popular Mobilisation forces from southern Iraq -- were suspended from a swingset-like metal structure by chains attached to their hands and feet, then set on fire.

IS, which overran large parts of Iraq last year and still controls much of the country's west, said the murders were in revenge for the alleged burning of four men by pro-government forces.

"Now retribution has come, for today, we will attack them as they attacked us, and punish them as they punished us," a masked militant says in the video.

The video was not dated and did not give a specific location for where the killings took place, but it did carry a tag indicating that it was produced by the IS media unit responsible for Iraq's Anbar province.

The video included a clip said to show a Sunni man suspended over a fire while still alive as pro-government forces look on, and another of famous Shiite fighter Abu Azrael ("Father of the Angel of Death") slicing a piece of flesh off a burned corpse with a sword.

IS has carried out a slew of atrocities in territory it controls in Iraq and Syria, such as mass executions and a campaign of killings, kidnapping and rape targeting minorities.

It has recorded many killings -- including beheadings, shootings, drownings and burnings -- in videos posted online.

Baghdad's forces regained significant ground from the jihadists in two provinces north of the capital with support from a US-led coalition and Iran, but much of western Iraq remains outside government control.

Australia urges more European nations to join IS air strikes
Sydney (AFP) Aug 31, 2015 - Australia on Monday urged more European nations to begin air strikes against Islamic State group in Syria and Iraq as a way of tackling the escalating refugee crisis gripping the continent.

Foreign Minister Julie Bishop said jihadists were responsible for driving hundreds of thousands of migrants to Europe and a broadening of the coalition fighting them was necessary.

"Over 40 percent of the people currently seeking asylum in Europe are from Syria, and we need a united front to defeat the terrorist organisations that are driving the displacement of so many people," she told reporters in Sydney.

"Already there are about 60 countries that are providing support in one way or another to the US-led coalition.

"But there's more countries can do in terms of supporting the air strikes which are proving effective in stopping Daesh (IS) from claiming territory off sovereign governments and from inflicting so much barbaric violence."

Bishop was even more explicit in an interview with The Australian newspaper, published Monday

"Countries adjoining Syria and Iraq, Lebanon, Jordan and others are bearing the brunt of millions of people fleeing into their borders and then into Europe," she said.

"That's why I believe the Europeans must be involved in the coalition air strikes and the effort in Syria and Iraq."

Only a handful of European nations are currently conducting air strikes against the jihadists, including France and Britain, as part of a coalition of Western and Arab powers.

Australia has six RAAF F/A18 combat jets and two support aircraft, based in the United Arab Emirates, taking part.

While Canberra has been carrying out air strikes in Iraq it has not targeted Syria so far, citing legal concerns, but is considering a request from the United States this month to extend its campaign into the war-torn country.

Bishop separately told Australia's Channel Ten that air strikes were a risky proposition.

"Some estimates say there are about 30,000 of these fighters who embed themselves in towns and cities. The difficulty for coalition air strikes is to not hit civilians and so they are limited in what they can do," she said.

"But Daesh is across both the Syrian and Iraq border. They have claimed that area.

"It's essentially ungoverned by either the Syrian regime or the Iraqi government. And that's why there's this request from the US for Australia to join the coalition, that is carrying out air strikes over the Syria-Iraq border."

European Union home affairs ministers are expected to hold emergency talks on September 14 in Brussels on the continent's escalating migration crisis, the Luxembourg government said on Sunday.

The number of migrants reaching the EU's borders reached nearly 340,000 during the first seven months of the year, up from 123,500 during the same period in 2014, according to the bloc's border agency Frontex.