Trump praises Saudi crackdown as bribe allegations emerge

Trump took to Twitter on Monday to praise Riyadh's leaders, as a Saudi whistleblower made allegations that the US president recently took a $1 billion bribe from the kingdom's powerful Crown Prince Mohammed bin Salman.

"I have great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing," Trump tweeted.

"Some of those they are harshly treating have been 'milking' their country for years!" added the US president, whose marathon Asia tour moves to South Korea on Tuesday.

The Trump administration had been silent about the unprecedented arrests of dozens of Saudi Arabia's most powerful princes, military leaders and ministers, which are widely being seen as a consolidation of power by the 32-year-old bin Salman.

The purge began on Saturday hours after an anti-graft commission headed by bin Salman was set up.

Among the more than 30 figures taken into custody at the Ritz-Carlton hotel in Riyadh were Prince al-Waleed bin Talal, one of the world's richest men and two of the late king Abdullah's sons.

Bin Talal strongly criticised Trump for his anti-Islamic rhetoric during the presidential campaign and even called for him to drop out of the race.

Trump's comments came hours after well-informed anonymous Saudi commentator who uses the Twitter handle Mujtahidd alleged that bin Salman personally bribed Donald Trump with $1 billion during the US president's visit to Riyadh in May.

Mujtahidd said Bin Salman, then-deputy crown prince, had used the bribe to win Trump's favour in a power struggle with his cousin Mohammed bin Nayef, who was heir to the throne until he was deposed in June.

The US and Saudi Arabia have historically enjoyed close ties, which Trump re-affirmed in May when he visited the country in his first foreign trip since taking office.

Washington and Riyadh announced contracts worth more than $380 billion, including a $110 billion arms deal aimed at countering perceived threats from Iran and "radical Islamists."

Trump spoke with King Salman over phone on Saturday, according to a readout from his office.

Trump lauded the monarch and his son's "recent public statements regarding the need to build a moderate, peaceful, and tolerant region" and urged the kingdom to choose Wall Street as a venue for the IPO of oil giant Aramco.