The Brussels attacks are a stark reminder that European countries need to step up their efforts against the Islamic State group, US Defense Secretary Ashton Carter said.

The United States has been pressing its European and Arab allies to contribute more to the US-led campaign against the group in Iraq and Syria.

The IS group has claimed responsibility for Tuesday's suicide bombings on the Belgian capital's airport and metro that killed 31 people and wounded another 300.

"The thing that I think the Brussels event is going to further signify to Europeans is that they — as we have been accelerating our campaign to defeat ISIL in Syria, in Iraq and elsewhere — they need to accelerate their efforts and join us," Carter told CNN on Wednesday.

"But (for) anyone doubting in Europe, it's a reminder that we have to accelerate our effort."

Washington has boosted its own special forces presence in Iraq and Syria, and is now letting its military advisers move closer to the frontlines.

A US Marine manning a newly established US artillery position in northern Iraq was killed over the weekend in a rocket attack, underscoring the risks.

Carter said he expected Mosul, a major IS bastion in northern Iraq, would be retaken by Iraqi troops within a year.

"If the Iraqi government continues to support their own armed forces and we continue to support them, there is no reason we have to wait a year for the collapse of Mosul," Carter said.

"But I'm not prepared to give you a timetable either. This is a war."

"I think we need to do and are doing everything we can to accelerate that schedule," he added, predicting that: "We'll be doing more."

The Iraqi forces, as they advance on Mosul will need air support, as well as training and equipment, Carter said.

"They need things like bridges to cross the Tigris River. They need lots of things," he added.

Iraq, meanwhile, announced Thursday it had launched the first phase of operations to retake Mosul.

It's in Mosul, Iraq's second largest city, that IS declared its Islamic "caliphate" in 2014.

Israeli defence chief calls Europe attacks 'World War III'
Jerusalem (AFP) March 24, 2016 –

Israeli Defence Minister Moshe Yaalon said Thursday that the deadly bombings in Brussels are evidence of a new world war, which the Jewish state and other countries must fight together.

"We're in the same boat," he told Israeli army radio in an interview.

"The world finds itself at the moment in a third world war, or as it has been called, 'a clash of civilisations'. We must face it together."

"We cooperate with Belgium and other European countries," he added. "We are on the same side, with shared values and interests."

The jihadist Islamic State group has claimed responsibility for Tuesday's attacks on the airport and a metro station in the Belgian capital that killed 31 people and wounded another 300.

Israel's intelligence minister on Wednesday accused Belgian leaders of laxity over the threat posed by homegrown Muslim radicals.

"If in Belgium they continue to eat chocolate, enjoy life and parade as great liberals and democrats while not taking account of the fact that some of the Muslims who are there are organising acts of terror, they will not be able to fight against them," Yisrael Katz told public radio.

Yaalon responded on Thursday by saying: "I would suggest not giving advice in public. And I'd be happy to eat dark Belgian chocolate."

Israeli former president and Nobel Peace Prize laureate Shimon Peres in Paris on Thursday asked local religious leaders to give their communities a message of peace.

"We gathered here today Jews, Muslims and Christians to say loud and clear that we must fight terror, we must go against those preachers who are using God's name in vain to promote bloodshed and incitement," a statement from his office quoted him as saying.

"There is no God in the heavens that permits terrorism, there is no God willing to murder the innocent — babies, children, here in Europe, in the Middle East or the rest of the world."