Oil prices rose to a one-month high on Monday due to concern that supplies from one of the world's leading oil exporters may be limited because of a strike by oil workers protesting rising fuel prices.

Reports from the African press say that the labor unions in Nigeria have called a general strike to start at midnight Thursday to protest the removal of price limits on fuel. The strike would be the second union-led strike in recent months over fuel prices.

In July Nigeria descended into chaos as the unions launched a nation wide strike over President Olesugun Obasanjo's decision on June 19 to slash the government subsidy on domestic fuel prices. Obasanjo said the hike was irreversible as the government could no longer subsidise fuel prices on which it already spends about 250 billion naira (1.95 billion dollars) annually.

This second strike threat comes after the Organization of Petroleum Exporting Countries (OPEC) agreed to reduce output at last months meeting in Vienna.

Combined with the disruption to Mexican exports due to tropical storm Larry and the resulting turmoil from Israel's aggressive venture into Syria there are now supply concerns from the world's key producers, forcing crude prices up to the $US31 mark again after several months of decline.

OPEC ministers have also agreed to meet in Vienna again on Dec. 4 to discuss oil prices and supplies, possibly alluding to another cut in production ahead of a perceived supply surplus in 2004.

The oil cartel produces about a third of the world's oil and aims to keep the price of a group of crude oils in a range of $22 to $28 a barrel. The index, known as the OPEC basket, rose 25 cents to $27.85 on Monday.