Fresh Iranian strikes on energy infrastructure and fears of a prolonged conflict have overshadowed the historic drawdown.

AFP explains why the release has not eased oil markets.

- Not enough oil -

International Energy Agency member countries agreed on Wednesday to release 400 million barrels of oil from their reserves -- the largest amount ever.

The IEA move was aimed at easing the immediate impact of the Middle East war on energy markets.

The United States alone, the biggest consumer and producer of crude, will gradually supply 172 million barrels over three months, or 40 percent of its current reserves.

But analysts said the move is too small to offset the disruption triggered by American-Israeli attacks against Iran on February 28.

The release falls "far short of the supply losses we are seeing from the Persian Gulf", noted commodities strategists at ING bank.

According to the IEA, daily global crude production is down at least 8.0 million barrels, with an additional 2.0 million related to petroleum products shut off.

"It seems unlikely that the flow of reserves can make up for the lost flow of production," said Neil Wilson, a strategist at Saxo UK investor.

"This is a temporary and limited solution -- the key is to reopen the Strait of Hormuz" which borders Iran and under normal circumstances allows for the passing of about one fifth of the world's crude.

- Infrastructure under attack -

Prices are jumping also on a fresh wave of Iranian strikes aimed at Gulf energy targets.

The IEA on Thursday warned that the war "is creating the largest supply disruption in the history of the global oil market".

Retaliatory missiles and drone attacks have brought shipping through the Strait of Hormuz almost to a halt.

Energy infrastructure across the region has also been targeted.

Bahrain said an Iranian attack hit fuel tanks in Muharraq on Thursday, while drones struck fuel tanks at Oman's Salalah port.

Saudi Arabia said it had intercepted two drones heading towards its Shaybah oil field.

Oil giants in the Gulf have meanwhile had to reduce their production owing to a lack of storage capacity.

- Prolonged war -

Markets are rattled additionally by the risk of conflict dragging on.

While US President Donald Trump has said the war could end "soon", Iran has warned it could wage a long conflict that would "destroy" the world economy.

"From a market perspective, the problem is that investors are increasingly pricing in a more protracted conflict that causes extensive economic damage," said Deutsche Bank analyst Jim Reid.

The IEA warned that there were "no signs of a de-escalation in hostilities or a clear timeline for a recovery in flows through the Strait".