LONDON/MOSCOW (Reuters) -Eight OPEC+ countries agreed on Thursday to advance their plan for oil output hikes by increasing oil output by 411,000 barrels per day in May, an unexpected decision that prompted oil prices to extend earlier losses.

Oil, which was already down over 4% on U.S. President Donald Trump's announcement of tariffs on trading partners, extended declines after OPEC updated its plans in a statement, with Brent crude dropping over 5% towards $70 a barrel.

Eight members of OPEC+, which includes the Organization of the Petroleum Exporting Countries and allies led by Russia, had been scheduled to raise output by 135,000 barrels per day in May as part of a plan to gradually unwind their most recent layer of output cuts.

But after a meeting of the eight countries held online on Thursday, the group announced it would boost output by 411,000 bpd in May. OPEC cited "continuing healthy market fundamentals and the positive market outlook."

"This comprises the increment originally planned for May in addition to two monthly increments," OPEC said in a statement referring to the volume. "The gradual increases may be paused or reversed subject to evolving market conditions."

The May hike is the next increment of a plan agreed by Russia, Saudi Arabia, UAE, Kuwait, Iraq, Algeria, Kazakhstan and Oman to gradually unwind their most recent output cut of 2.2 million bpd, which came into effect this month.

The eight countries will meet on May 5 to decide on June output, OPEC's statement said.

OPEC+ also has 3.65 million bpd of other output cuts in place until the end of next year to support the market.