President Donald Trump voiced his approval Monday for the weekend political purge in Saudi Arabia that, while ostensibly part of an anticorruption crackdown, is widely seen by analysts as a move by the kingdom’s crown prince to consolidate power.

“I have great confidence in King Salman and the Crown Prince of Saudi Arabia, they know exactly what they are doing,” Trump tweeted Monday from Japan. “Some of those they are harshly treating have been ‘milking’ their country for years!”

On Saturday, more than five dozen Saudi princes, ministers and prominent businessmen, including billionaire investor Prince Alwaleed bin Talal, were arrested. Alwaleed has a number of large holdings in Western companies, such as Citigroup Inc. C, -1.47% , eBay Inc. EBAY, -0.06% , Apple Inc. AAPL, -3.17% and Twitter Inc. TWTR, +2.03% . Separately, another Saudi prince was killed in an unexplained helicopter crash Sunday near the country’s border with Yemen.

The roundup is seen by many as a move by Crown Prince Mohammed bin Salman, the heir to the Saudi throne, to consolidate power as he moves to make sweeping changes to the country.

Read: What Saudi Arabia’s purge of ministers, princes — including the Buffett of the Middle East — means for markets

U.S. and global oil futures shot up Monday with their sharpest daily gains, in dollar terms, in about a year.

Tensions in Saudi Arabia were further strained Monday after a top minister said Lebanon has declared war against it. That comes after Friday’s surprise resignation of Lebanon’s Saudi-backed prime minister, Saad Hariri, as he was visiting the Saudi capital of Riyadh. In Lebanon, Iran backs Hezbollah, a group that Hariri and the Saudis oppose.

And on Saturday, a ballistic missile fired from Yemen — reportedly by Iran-backed rebels — was intercepted over Riyadh. On Monday, Saudi Arabia blamed Iran and called it an “act of war.”

Iran on Monday accused the U.S. of fomenting turmoil in the region, with Foreign Minister Mohammad Javad Zarif tweeting that a recent visit by top Trump adviser Jared Kushner led to Hariri’s resignation in a move to destabilize the region.

Kushner took an unannounced trip to Saudi Arabia at the end of October, Politico reported last week. A source told Politico that Kushner’s trip was to advance peace in the Middle East.

Trump visited Saudi Arabia in May, just weeks before a coalition of Mideast countries, including Saudi Arabia, Bahrain, Egypt, Yemen and the United Arab Emirates, accused Qatar of backing terrorist activities and blockaded the small Gulf state, creating a rift between important U.S. allies in the region. Trump also met Bahrain’s king during his Saudi trip, and soon after that Bahrain violently cracked down on internal opposition.