Oil prices hit their highest levels since July 2015 early on Monday as markets tightened, while Saudi Arabia's crown prince cemented his power over the weekend through an anti-corruption crackdown that included high-profile arrests.

Brent futures, the international benchmark for oil prices were as high as $62.90 per barrel by 0750 GMT on Monday, their highest level since July 2015. This is over 40 percent above June's 2017 lows.

US West Texas Intermediate (WTI) crude rose above $56 per barrel in afternoon trading, also the highest since July 2015, and was at $56.15 at 0750 GMT. WTI is one-third higher than its 2017 lows.

Crown Prince Mohammed bin Salman, also known as MBS, has tightened his grip on power through an anti-corruption purge by arresting royals, ministers and investors including prominent business billionaire Alwaleed bin Talal and the head of the National Guard, Prince Miteb bin Abdullah.

RBC Capital Markets said in a note that although the “purge represents a stunning political development in Saudi Arabia,” it expected “no immediate changes” in the oil policy of Saudi Arabia, which is the world's biggest exporter of crude oil.