A team of investigators has entered the Saudi consulate in Istanbul for what Turkish officials called a joint inspection of the building where Saudi journalist Jamal Khashoggi disappeared nearly two weeks ago.

The team arrived in unmarked police cars at the consulate and said nothing to journalists waiting outside as they entered the building.

Police then pushed back journalists from the front of the consulate, where they have been stationed for days, setting up a new cordon to keep them away.

Members of the media on the blocked road leading to Saudi Arabia's consulate in Istanbul
Members of the media on the blocked road leading to Saudi Arabia’s consulate in Istanbul (Emrah Gurel/AP)

International concern continues to grow over the writer’s October 2 disappearance.

American politicians have threatened tough punitive action against the Saudis, and Germany, France and Britain have jointly called for a “credible investigation” into Mr Khashoggi’s disappearance.

A Foreign Ministry official had earlier said the team would visit the diplomatic post on Monday.

Turkish officials have said they fear a Saudi hit team that flew into and out of Turkey on October 2 killed and dismembered Mr Khashoggi, who had written Washington Post columns critical of Saudi Crown Prince Mohammed bin Salman.

The kingdom has called such allegations “baseless” but has not offered any evidence Mr Khashoggi ever left the consulate.

Such a search would be an extraordinary development, as embassies and consulates under the Vienna Convention are technically foreign soil.

Security guards enter Saudi Arabia's consulate
Security guards enter Saudi Arabia’s consulate (Petros Giannakouris/AP)

Saudi Arabia may have agreed to the search in order to appease its Western allies and the international community.

However, it remained unclear what evidence, if any, would remain nearly two weeks after Mr Khashoggi’s disappearance.

A cleaning crew with mops and rubbish bags walked in past journalists waiting outside the consulate.

US President Donald Trump has said Saudi Arabia could face “severe punishment” if it was proven it was involved in Mr Khashoggi’s disappearance.

Mr Trump tweeted on Monday that he had spoken with Saudi King Salman, “who denies any knowledge” of what happened to Mr Khashoggi.

“He said that they are working closely with Turkey to find answer,” Mr Trump wrote.

“I am immediately sending our Secretary of State (Mike Pompeo) to meet with King!”

On Sunday, Saudi Arabia warned that if it “receives any action, it will respond with greater action, and that the kingdom’s economy has an influential and vital role in the global economy”.

“The kingdom affirms its total rejection of any threats and attempts to undermine it, whether by threatening to impose economic sanctions, using political pressures or repeating false accusations,” said the statement, carried by the state-run Saudi Press Agency.

The statement did not elaborate but a column published in English a short time later by the general manager of the Saudi-owned Al-Arabiya satellite news network suggested Saudi Arabia could use its oil production as a weapon.

Benchmark Brent crude is trading at around 80 dollars a barrel and Mr Trump has criticised Opec and Saudi Arabia over rising prices.

Already, international business leaders are pulling out of the kingdom’s upcoming investment forum, a high-profile event known as Davos in the Desert, though it has no association with the World Economic Forum.

They include the chief executive of Uber, a company in which Saudi Arabia has invested billions of dollars; billionaire Sir Richard Branson; JPMorgan Chase & Co chief executive Jamie Dimon; and Ford Motor Co executive chairman Bill Ford.

News that the chief executive of Uber, Dara Khosrowshahi, would pull out of the conference drew angry responses across the region.

The foreign minister of the neighbouring island kingdom of Bahrain, Khalid bin Ahmed Al Khalifa, tweeted that there should be a boycott of the ride-hailing app both there and in Saudi Arabia.

Late on Sunday, Saudi King Salman spoke by telephone with Turkish President Recep Tayyip Erdogan about Mr Khashoggi.

Turkish police officers arrive at the Saudi Arabia consulate
Turkish police officers arrive at the consulate (Emrah Gurel/AP)

Turkey said Mr Erdogan “stressed the forming of a joint working group to probe the case”.

Saudi Arabia, meanwhile, said King Salman thanked Mr Erdogan “for welcoming the kingdom’s proposal” for forming the working group.

The king said Turkey and Saudi Arabia enjoy close relations and “that no-one will get to undermine the strength of this relationship”, according to a statement on the state-run Saudi Press Agency.

While Turkey and the kingdom differ on political issues, Saudi investments are a crucial lifeline for Ankara amid trouble with its national currency, the Turkish lira.

Mr Khashoggi has written extensively for the Post about Saudi Arabia, criticising its war in Yemen, its recent diplomatic spat with Canada and its arrest of women’s rights activists after the lifting of a ban on women driving.

Those policies are all seen as initiatives of the crown prince.