Oil eased on Tuesday, after having posted its largest gain in six weeks the previous day, while tension flared between Saudi Arabia and Iran, just as the Saudi crown prince tightened his grip on power.
U.S. West Texas Intermediate (WTI) crude ended Tuesday's session down 15 cents at $57.20 a barrel. It settled at the highest level since June 2015 in the previous session.
Brent crude futures were down 57 cents at $63.70 a barrel by 2:29 p.m. ET (1829 GMT), having closed 3.5 percent higher on Monday, marking the biggest percentage gain in about six weeks.
Saudi Crown Prince Mohammed bin Salman moved to shore up his power base with the arrest of royals, ministers and investors, which an official described as part of "phase one" of the crackdown.
More tellingly, tensions escalated between OPEC members Saudi Arabia and Iran and it was this, more than the purge, that rattled the oil market, analysts said.