LONDON, June 20: Oil prices fell heavily on Wednesday after the US government said that its energy stockpiles had risen strongly last week, offsetting concerns about a nationwide strike in crude producer Nigeria.

Brent North Sea crude for August delivery dived $1.74 to $70.10 per barrel in electronic deals.

New York's main oil futures contract, light sweet crude for delivery in July, shed $1.35 to $67.75 per barrel in pit trading.

“A sharp increase in crude supplies is weighing on the market, which had been worried about increased supply disruption from Nigeria,” said Tom Hartmann, a trader at Altavest.

The US Department of Energy said that stockpiles of crude oil grew by 6.9 million barrels in the week to June 15. Analysts had forecast a drop of 50,000 barrels.

“Some of the large build in stockpiles can be attributed to supplies that had been sitting offshore last week and were not counted in last week's inventory numbers,” Hartmann added.

—AFP