Shares in Asia fell broadly on Thursday, as oil prices leapt 9% to above $100 a barrel on reports of more ships hit in Gulf waters and the closure of oil terminals.
Investors took little comfort from the International Energy Agency's plan to release 400 million barrels of oil from its reserves, the largest such move in its history.
Both oil benchmarks were up 9%, with Brent crude futures at $100.22 a barrel, extending a rise of more than 4% overnight.
US crude futures were at $95.41 a barrel.
Shares slid, with MSCI's broadest index of Asia-Pacific shares outside Japan falling 1.6%, while the Nikkei dropped 1.5%.
Chinese blue-chips lost 0.6% and Hong Kong's Hang Seng index skidded 1.2%.
Two fuel tankers in Iraqi waters had been struck by explosive-laden Iranian boats, Iraqi security officials said early on Thursday.
Iran had earlier stepped up attacks on merchant ships in the Strait of Hormuz, telling the world to get ready for oil at $200 a barrel.
