Turkey has arrested two men suspected of spying for the United Arab Emirates and is probing if they are tied to Saudi journalist Jamal Khashoggi's murder, Anadolu state news agency said on Friday.

Members of the Saudi team that killed journalist Jamal Khashoggi received training in the United States, the Washington Post has reported, revealing other new elements in the death of the newspaper's former contributor.

The European Parliament on Tuesday heard, for the first time, "horrific testimonies" by two of the victims of the unjust blockade imposed on Qatar and three others who have also been victims of violations of human rights by Saudi Arabia, the UAE and Bahrain.

Turkish President Tayyip Erdogan urged the United States to put its weight behind the investigation into the killing of Saudi journalist Jamal Khashoggi and not to set the matter aside because of its ties with Riyadh.

President Donald Trump appeared prepared to ignore the US Congress's Friday deadline to determine who ordered the assassination of Jamal Khashoggi amid new revelations that Saudi Arabia's crown prince spoke of threatening the journalist with a "bullet."

A United Nations investigation into the killing of Saudi journalist Jamal Khashoggi has to be launched, Turkish Foreign Minister Mevlut Cavusoglu said on Friday.

The Turkish fiancee of murdered Saudi journalist Jamal Khashoggi said Friday she hoped pressure from the US Congress would encourage the Trump adminstration to take a tougher stance on the killing.

The UN investigator leading the inquiry into the killing of Jamal Khashoggi said on Tuesday that Saudi Arabia had not yet approved a request for her to enter the kingdom's consulate in Istanbul and meet Saudi authorities.

A key US senator Saturday said the Saudi crown prince was responsible for Jamal Khashoggi's murder and must be "dealt with", as he threatened new sanctions.

The US does not believe the official Saudi version of the murder of the Washington Post columnist and dissident Jamal Khashoggi is credible, a senior administration official has said.

UN chief Antonio Guterres called Sunday for a "credible" probe into journalist Jamal Khashoggi's murder in Saudi Arabia's consulate in Istanbul.

US Secretary of State Mike Pompeo defended the Trump administration's handling of the killing of Saudi journalist Jamal Khashoggi on Wednesday, stressing Saudi Arabia's importance as a US ally against Iran.