Saudi Crown Prince Mohammed bin Salman embarked Thursday on a regional tour starting with the United Arab Emirates, his first official trip abroad since critic Jamal Khashoggi's murder tipped the kingdom into crisis.

Prince Mohammed will visit a "number of brotherly" Arab states at the request of his father, King Salman, the royal court said in a statement carried by the official Saudi Press Agency, without naming the countries.

Abu Dhabi's Crown Prince Mohammed bin Zayed welcomed him on his first stop in the UAE, a close ally that is part of a Saudi-led coalition battling Iran-aligned Huthi rebels in Yemen, according to the Emirati state news agency WAM.

The two leaders discussed "regional and international" developments and the "challenges and threats facing the Middle East region", WAM said, without elaborating.

The prince is also set to travel to the Tunisian capital on Tuesday, a presidential source in Tunis told AFP.

The regional tour, just before the crown prince is expected to attend the G20 summit in Argentina next week, comes as international pressure has mounted on Riyadh over the grisly murder of Washington Post columnist Khashoggi in the Saudi consulate in Istanbul on October 2.

The Saudi insider-turned-critic was killed and dismembered in what Saudi Arabia said was a "rogue" operation, but CIA analysis leaked to the US media pointed the finger at Prince Mohammed.

US President Donald Trump on Tuesday glossed over the CIA's reported conclusion that the crown prince had authorised the killing, saying Washington would not slacken its support for the kingdom.

PRINCE AND ERDOGAN COULD MEET

Turkey's President Recep Tayyip Erdogan could meet with Prince Mohammed on the sidelines of the G20 summit, according to a Turkish presidential spokesman.

Such a meeting would be the first face-to-face encounter between the two since the killing that has tainted the image of both the crown prince and the kingdom.

Erdogan has said the order to murder Khashoggi came from "the highest levels" of the Saudi government but has stopped short of directly blaming Prince Mohammed.

Saudi Arabia has said that 21 people are in custody, with death penalties sought against five men, but attention remains focused on whether the crown prince ordered the murder despite the kingdom's denials.

The European Union on Thursday called for those "really responsible" to be held to account.

Calling for a "completely transparent and credible investigation", the EU's top diplomat Federica Mogherini said: "For us accountability does not mean revenge."

Saudi Foreign Minister Adel al-Jubeir on Wednesday said criticism of Prince Mohammed is a "red line", and that calls for him to be held accountable for the murder would not be tolerated.

But keeping up the international pressure on Riyadh, Denmark on Thursday suspended arms sales to Saudi Arabia over the murder, the second country to do so after Germany.

Separately on Thursday, the French foreign ministry said it would impose sanctions against 18 Saudi citizens over Khashoggi's murder.