Saudi state TV showed footage of the crown prince's plane arriving in Nouakchott.
Prince Mohammed, on his first foreign tour since the October 2 murder of Saudi journalist Jamal Khashoggi, held talks instead with Prime Minister Ahmed Ouyahia, Algeria's presidency said, during a low-key visit that was kept largely out of the media spotlight.
After Mauritania, he is due to visit Algeria.
With its traditionally neutral stand, Algiers has good relations with Saudi Arabia's regional rival Iran but has also maintained cordial ties with Riyadh. "I think we're going to see definitely some return to institutionalism, some return to a consensus-based decision-making process and commitment to defined procedures".
"I spoke to the crown prince to highlight our concerns and the need for better answers on the killing of Khashoggi and the need for cease fire in Yemen", Trudeau said.
"What we have said, both within the European Union (EU), as well as bilaterally to Saudi Arabia, is that we have to clarify what has happened", Sanchez said while attending the G20 summit in Buenos Aires. Trump has said it may never be known if MBS ordered the killing or not.
Khashoggi's killing has put mounting pressure on Riyadh and MbS, who Turkish officials - and reportedly the Central Intelligence Agency - have concluded ordered the critic's death.
U.S. Secretary of State Mike Pompeo doubled down on U.S. support for the crown prince on Saturday, saying there was "no direct evidence" linking MBS to the murder of Khashoggi.
Trump's contention that "maybe he did, maybe he didn't" order the killing appears to have helped pave the way for the crown prince's return to global forums.
"And when it is done, when you complete that analysis, there's no direct evidence linking him to the murder of Jamal Khashoggi".
"He is like a beast "pac man" the more victims he eats, the more he wants", Khashoggi said in the messages to Abdulaziz. Saudi Arabia later announced that the journalist had been killed in a fight in the diplomatic mission.
Khashoggi's killing was an "ugly crime" that pushed Jordanians of all walks of life to oppose binSalman's visit, he said. Abdulaziz on Sunday launched a lawsuit against an Israeli company that invented the software he believes was used to hack his phone.