World leaders on Wednesday (January 8th) condemned Iran's missile attack on Iraqi bases housing US and other foreign troops and urged an end to the escalating confrontation between Tehran and Washington.

Iran said it had acted to avenge the US killing of Islamic Revolutionary Guard Corps Quds Force (IRGC-QF) commander Qassem Soleimani last week.

The Pentagon said it was still "working on initial battle damage assessments", with no immediate reports on casualties.

The Iraqi military said it sustained no casualties in 22 missile strikes on bases housing US troops.

"I condemn the Iranian missile attacks on US and coalition forces in Iraq. NATO calls on Iran to refrain from further violence," NATO chief Jens Stoltenberg said.

"Allies continue to consult and remain committed to our training mission in Iraq," he added in a social media post.

The 500-strong NATO mission has suspended training activities due to the increased security risks, but Stoltenberg has said it will resume when the situation improves.

A NATO official said none of its troops in Iraq had been hurt in the strikes. The alliance had said Tuesday it would take some personnel out of the country for safety reasons.

'Urgent de-escalation'

"Iran should not repeat these reckless and dangerous attacks but should instead pursue urgent de-escalation," Britain's Prime Minister Boris Johnson told parliament.

Foreign Secretary Dominic Raab warned that another war in the Middle East would only benefit the "Islamic State of Iraq and Syria" (ISIS) "and other terrorist groups".

EU foreign policy chief Josep Borrell said it is "in no-one's interest to turn up the spiral of violence even further", warning that the crisis was hampering the fight against ISIS.

EU foreign ministers are holding emergency talks on the Iran crisis on Friday to discuss what the bloc can do to reduce tensions.

European Commission President Ursula von der Leyen, who will raise the situation when she meets the British Prime Minister in London later Wednesday, said "the use of weapons must stop" to allow space for dialogue.

French Foreign Minister Jean-Yves Le Drian called for a de-escalation.

"France remains determined to work to ease tensions and is in contact with all the parties to encourage restraint and responsibility," he said.

End to 'spiral of conflict'

Germany's defence minister Annegret Kramp-Karrenbauer strongly condemned the attack and called on Iran to end a "spiral" of conflict.

Kramp-Karrenbauer said Germany had been in contact with the US department of defence throughout Tuesday night, and that "all channels" of communication would be opened in a bid to prevent further escalation.

She added that she would seek a meeting of the international coalition's 13 framework nations to discuss the situation in the region.

Chancellor Angela Merkel's spokesman said all parties needed to "exercise restraint and to turn away from a logic of escalation and towards a logic of dialogue".

Germany temporarily withdrew 32 of its soldiers from a camp close to Baghdad on Tuesday.

Israeli Prime Minister Benjamin Netanyahu made it clear Israel would strike back if attacked.

"Anyone who attacks us will receive a resounding blow," he said.

Threats from pro-Iran factions

A top commander of Iraq's paramilitary Popular Mobilisation Forces (PMF) on Wednesday called for an "Iraqi response" to the strike that killed Soleimani and PMF deputy chief Abu Mahdi al-Muhandis.

"That response will be no less than the size of the Iranian response. That is a promise," hardline PMF commander Qais al-Khazali threatened on social media.

The Iran-backed Iraqi militia Harakat al-Nujaba vowed revenge for al-Muhandis.

On Tuesday, Harakat al-Nujaba head Akram al-Kaabi said pro-Iran groups had further unified their ranks to respond to the US.

His deputy had earlier called for an urgent meeting to unite anti-US forces across Iraq.