U.S. crude futures' August contract, the new front month from Wednesday, climbed 35 cents to $50.20 a barrel by 06:04 GMT, marking its first rise above $50 since June 10, as reported by Reuters.
Brent crude futures were up 32 cents at $50.94 a barrel.
U.S. crude inventories fell by 5.2 million barrels for the week ended June 17, the API said. The trade group's figures were triple the draw of 1.7 million barrels forecast by analysts in a Reuters poll.
Read alsoECB chief highlights growth risks, uncertaintyThe U.S. government's Energy Information Administration will issue official stockpile data on Wednesday.
Markets remain jumpy over the possibility the United Kingdom will vote to leave the European Union on Thursday in a referendum, with polls showing little difference between the "remain" and "leave" camps.
