SAUDI Arabia's explanation about the murder of journalist Jamal Khashoggi "lacks credibility," Theresa May told King Salman in a personal phonecall, insisting Britain had "grave concerns" about what some regard as a state-sponsored killing.

In the call to the head of state, the Prime Minister also made clear that all of the Saudi murder suspects would be banned from entering the UK and would have their visas revoked.

Riyadh at first denied any knowledge of or responsibility for the killing of Mr Khashoggi but later said he had died in a fight at its consulate in Istanbul.

A Downing Street spokesman said: “The Prime Minister said the current explanation lacks credibility so there remains an urgent need to establish exactly what happened. She strongly urged Saudi Arabia to co-operate with the Turkish investigation and to be transparent about the results. It is important that the full facts are established.”

Mrs May’s blunt message to King Salman came after Crown Prince Mohammed bin Salman made his first public remarks about the killing since Mr Khashoggi entered the Saudi consulate in Istanbul on October 2, where he was murdered.

The prince said the killing of Mr Khashoggi was a "heinous crime that cannot be justified" and that it would not be allowed to "drive a wedge" between Turkey and Saudi Arabia.

His comments came at the Future Investment Initiative business conference, which several foreign ministers, including Liam Fox, the International Trade Secretary, have boycotted.

The Prince Salman said his "war" was restoring the Middle East to its past glory and received a standing ovation for the comment. He did not mention Saudi Arabia's conflict with Yemen.

Over 10,000 people have been killed in Yemen's civil war, which has displaced two million more and helped spawn a cholera epidemic. Saudi-led air strikes have struck medical clinics and markets, killing large numbers of civilians and damaging vital infrastructure.

In the Commons, Ian Blackford, the SNP leader, said Mr Khashoggi’s killing had "all the hallmarks of being a premeditated murder" and urged Mrs May to follow the “moral leadership” of Germany’s Angela Merkel in announcing that Whitehall would not approve any new arms sales to Riyadh.

“The UK Government must take decisive action; words of condemnation will not do," declared the Highland MP.

He went on: “The Saudi Arabian regime is responsible for multiple human rights violations: critics face death by crucifixion; teenagers are tortured and women are imprisoned for campaigning for their human rights.

“The brutal bombardment of Yemen is pushing that country to the brink of famine and now we have the state-sponsored murder of Jamal Khashoggi. What more evidence of criminality does the Prime Minister need before she fully commits to ending the sale of arms to the brutal regime in Saudi Arabia?”

The PM stressed how the UK had condemned the journalist’s killing “in the strongest possible terms” and had called for a “full and credible investigation”.

She told MPs: "The claim that has been made that Mr Khashoggi died in a fight does not amount to a credible explanation so there does remain an urgent need to establish what has happened in relation to this."

Mrs May said Sajid Javid, the Home Secretary, was "taking action against all suspects to prevent them entering the UK" and that “if these individuals currently have visas, those visas will be revoked today".

This announcement on the visas followed similar measures taken by the US.

Yet the SNP came under fire itself, being accused of “rank hypocrisy” after condemning UK arms sales to Saudi Arabia.

Ross Greer, the Scottish Greens’ international relations spokesman, said the Scottish Government was “only too happy to throw cash at” firms which helped construct deadly weapons used by the desert kingdom.

Figures released earlier this year showed the administration in Edinburgh spent £1.2 million supporting businesses involved in the arms trade in 2016/17 alone.

Raytheon – which is involved in making missiles linked to civilian deaths in Yemen – has been handed £185,625 of public cash since 2014. It has a factory in Glenrothes.

Mr Blackford insisted this money was given “on the basis of diversification away from the production of arms”. SNP ministers have also said the Scottish Government does not provide funding for the manufacture of munitions.

Meanwhile, Labour also demanded an immediate end to arms sales to Saudi Arabia with a spokesman for Jeremy Corbyn saying investment in manufacturing and skills would "more than offset" any potential job losses.

"There is a clear responsibility on the British Government to take decisive action in relation not only to the murder in Istanbul but also the conduct of the Yemen war," he declared.

The steps taken by the Conservative Government "do not go far enough in response to this action and the wide mass abuse of human rights by the Saudi dictatorship", added the spokesman.