A Web posting by a Saudi wing of a terrorist group al Qaeda called for attacks on oil suppliers to the United States. This includes Canadian oil facilities, among others.

The posting in e-magazine Sawt al-Jihad (Voice of Holy War) used by Islamist militants, also pointed to Venezuela and Mexico as big oil suppliers to the United States. Al Qaeda claimed responsibility for the foiled suicide bombing of Saudi oil installations in Abqaiq in February 2006.

"We should strike petroleum interests in all areas that supply the United States," said the message.

Canada is the largest oil and gas supplier to the United States, shipping well over half its daily production of about 2.5 million barrels of oil to the US via pipelines.

Canada's oil and gas industry regulators, including the National Energy Board and Alberta Energy and Utilities Board, are taking a threat by al Qaeda seriously on Wednesday, but had not raised security levels.

"Given the nature of the threat, there is really no direct evidence that Alberta infrastructure is being targeted and clearly, the information we get from intelligence agencies is what we base our decisions on," Alberta EUB spokesman Darin Barter said to Reuters.

Meanwhile, world oil prices dropped heavily Wednesday on news that U.S. stockpiles of distillates had fallen lower than expected last week, analysts said.