Australian Special Forces will travel to the Middle East this week to join a US-led international coalition against the Islamic State (IS) terrorist group, Prime Minister Tony Abbott said Monday.

Once in position, about 600 Australian troops will await orders to support Iraqi and Kurdish Peshmerga forces battling the militants, Xinhua reported.

Abbott described IS’s beheading of a third hostage, British aid worker David Haines, as pure evil.

“The beheading of a British aid worker is further demonstration this particular terrorist group does not just do evil, but exults in doing evil,” Abbott said.

Abbott said Australia would also send eight Super Hornet fighter-bombers, a Wedgetail airborne early warning and control aircraft, and a KC30 multi-role tanker and transport aircraft.

Australian instructors home after gaining frontline experience in Afghanistan would help train the Kurdish Peshmerga forces providing the main opposition to the IS, as well as members of the Iraqi army.

Abbott said the new operation was likely to take many months.

“I have to warn the Australian people that, should this preparation and deployment extend into combat operations, this could go on for quite some time — months rather than weeks, perhaps many, many months indeed,” Abbott said.

“My conversation with (US) President (Barack) Obama a few days ago certainly gave me to understand that the president is prepared for quite a lengthy American contribution to this particular mission.

“The ISIL (the former abbreviation of the IS) death cult threatens the people of Iraq, the region and the wider world.”

The Royal Australian Air Force (RAAF) will continue its humanitarian and military resupply missions using its giant C17 Globemaster and C130 Hercules transport aircraft.

Australia’s decision to take on a more active role in Iraq follows a formal request for help from the government of new Iraqi Prime Minister Haider al-Abadi as well as from the US.

“In recent days, I have discussed the situation with President Barack Obama, with Iraq’s new Prime Minister Haider al-Abadi and with Crown Prince Sheikh Mohammed bin Zayed of the United Arab Emirates,” Abbott said.

“These leaders share the government’s grave concern about the situation in Iraq and support Australian participation in an international coalition to disrupt and degrade ISIL’s ruthless advance.

“We are not deploying combat troops, but contributing to international efforts to prevent the humanitarian crisis deepening,” he said.