Saudi Arabia has detained three senior Saudi princes including Prince Ahmed bin Abdulaziz, the younger brother of King Salman, and Prince Mohammed bin Nayef, the king's nephew, for allegedly planning a coup, sources with knowledge of the matter said.
Crown Prince Mohammed bin Salman, King Salman's son and de facto ruler of the country, which is the world's top oil exporter and a key U.S. ally, has moved to consolidate power since ousting Mohammed bin Nayef as heir to the throne in a 2017 palace coup.
Later that year, he arrested several royals and other prominent Saudis, holding them for months at Riyadh's Ritz Carlton hotel, in an anti-corruption campaign that caused shockwaves at home and abroad.
Four sources told Reuters that Prince Ahmed and Mohammed bin Nayef were detained in the latest operation. Two sources, including a regional source, said Mohammed bin Nayef and his half-brother, Nawaf, were detained while at a private desert camp on Friday.
Crown Prince Mohammed, who is also referred to as MbS, "accused them (the princes) of conducting contacts with foreign powers, including the Americans and others, to carry out a coup d'etat," the regional source said.
"With these arrests, MbS consolidated his full grip on power. It's over with this purge," the source added, indicating that no rivals remain to challenge his succession to the throne.
Another source said the princes were accused of "treason".
The Saudi government media office did not respond to a Reuters request for comment on the detentions, which were first reported by The Wall Street Journal.
The regional source said King Salman had approved the latest detentions.
"The king signed off on the arrests," the source said, adding that the king is in a mental and physically sound state.
The king met British Foreign Secretary Dominic Raab on Thursday in the Saudi capital Riyadh. Both King Salman and the crown prince attended a cabinet meeting on Tuesday.
Crown Prince Mohammed, 34, has fuelled resentment among some prominent branches of the ruling family by tightening his grip on power. Some critics have questioned his ability to lead after the 2018 murder of a prominent journalist by Saudi agents and the largest-ever attack on Saudi oil infrastructure last year, sources have said.
They said royals seeking to change the line of succession view Prince Ahmed, King Salman's only surviving full brother, as a possible choice who would have support of family members, the security apparatus, and some Western powers.
Saudi authorities have not commented on issues of succession or criticism of the crown prince's leadership. Prince Mohammed is popular among Saudi youth and also has staunch supporters within the royal Al Saud family, which numbers around 10,000 members.
Saudi insiders and Western diplomats say the family is unlikely to oppose the crown prince while the 84-year-old king remains alive, saying the monarch is unlikely to turn against his favourite son, to whom he has delegated most responsibilities of rule.
Prince Ahmed has largely kept a low profile since returning to Riyadh in October 2018 after 2-1/2 months abroad and Saudi watchers have said there is no evidence he is willing to take the throne. During that trip abroad, he appeared to criticize the Saudi leadership while responding to protesters outside a London residence chanting for the downfall of the Al Saud dynasty.
Ahmed was one of only three people on the Allegiance Council, made up of the ruling Al Saud family's senior members, who opposed Mohammed bin Salman becoming crown prince in 2017, sources have earlier said.
Mohammed bin Nayef's movements have been restricted and monitored since then, sources have previously said.
The latest detentions come at a time of heightened tension with rival Iran and as the crown prince implements social and economic reforms, including an initial public offering by oil giant Saudi Aramco on the domestic bourse last December. Saudi Arabia is also the current chair for the Group of 20 major economies.
The crown prince has been lauded at home for easing social restrictions in the conservative Muslim kingdom and trying to diversify the economy away from oil.
But he has come under international criticism over a devastating war in Yemen, the murder of journalist Jamal Khashoggi in the kingdom's Istanbul consulate, and the detention of women's rights activists seen as part of a crackdown on dissent.