Britain is carrying out a review of arms sales to its NATO ally, its chief diplomat said.

"We will keep our defence exports to Turkey under very careful and continual review," Foreign Secretary Dominic Raab said in a statement to parliament.

"No further export licences to Turkey for items which might be used in military operations in Syria will be granted while we conduct that review."

Spain, a major arms exporter to Turkey, similarly announced a halt to sales of military material.

Spain's Socialist government asked Turkey to "put an end to this military operation", saying it "endangered regional stability", increased the number of refugees and threatened Syria's territorial integrity.

"In coordination with its European Union partners, Spain will deny new export licences for military equipment that can be used in the operation in Syria," a foreign ministry statement said.

"Turkey's legitimate security concerns must be addressed and resolved by political and diplomatic means, not by military actions."

Spain was Turkey's fifth biggest arms supplier between 2008 and 2018 after the United States, South Korea, Germany and Italy, according to the Stockholm International Peace Research Institute.

The announcements from London and Madrid follow similar moves by key European and NATO allies, including Germany -- one of Ankara's main arms suppliers -- and France.

- 'Many NATO allies are very critical' -

Sweden also announced it had halted exports of military equipment.

"Two permits that have been active have now been recalled regarding other military equipment," Carl Johan Wieslander, acting director of the Inspectorate of Strategic Products (ISP) that deals with such exports, told AFP.

Wieslander did not specify what type of kit the permits covered, but said they did not include anything that they referred to as "combat military equipment," meaning no weapons.

Ankara's assault against Kurdish forces launched last week has prompted a chorus of international condemnation.

In London, Raab said it had "seriously undermined the security and stability of the region".

"This is not the action we expected from an ally, it is reckless, counterproductive, it plays straight into the hands of Russia and the Assad regime," he told lawmakers.

NATO Secretary General Jens Stoltenberg discussed the volatile situation with British Prime Minister Boris Johnson in Downing Street on Tuesday.

Speaking after the meeting, Stoltenberg said the arms suspensions showed "many Nato allies are very critical and are condemning the military operation in northern Syria".

Meanwhile US President Donald Trump warned Monday that Turkey faces imminent sanctions over its actions but also signalled that Washington would avoid any armed conflict with Ankara.

Turkey's President Recep Tayyip Erdogan has said threats of sanctions and arms embargoes by Western powers will not stop the military offensive.

He vowed to continue the operation targeting the Syrian Kurdish People's Protection Units (YPG), which it sees as a "terrorist" off-shoot of Kurdish insurgents in its own territory, until "our objectives have been achieved".

Erdogan has said he wants to establish a safe zone stretching across northern Syria, to which it can repatriate many of the 3.6 million refugees that it is hosting from the Syrian conflict.

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