Renewed violence in Iraq has pushed oil prices to new records, nearing the $50-a-barrel mark.

US crude oil futures were at a closing high of $48.70 on Thursday, following threats of militia attacks on Iraqi pipelines, the 14th trading session out of 15 on the New York Mercantile Exchange to register a new high.

And once Asian trade kicked in, the price spiraled by another 28 cents, bringing the contract closer to the key $50 mark.

OPEC president Purnomo Yusgiantoro admitted concerns, but said that the cartel will wait until September before acting.

"I am concerned to see oil prices continuing to increase. But at the moment, we have not seen cost-pushed inflation," he said.

The latest surge was triggered by news that Shia militants loyal to radical cleric Moqtada Sadr had broken into the South Oil Company's headquarters and - according to witnesses, set it on fire.

When adjusted for inflation, oil prices remain below the all-time high they reached in the wake of the Islamic revolution in Iran in 1979. Then, a barrel of crude was worth about $80 in today's terms.

In London, Brent crude was also higher on Thursday, climbing $1.32 cents to $44.35.