The price of Brent crude oil surged to a nine-month high on Thursday, propelled by intensifying Iran concerns amid reports that Japan wanted to slash its Iranian crude imports, traders said.

Brent North Sea crude for delivery in April soared as high as $124.09 per barrel, reaching a level last seen on May 3, 2011. It later pulled back to $123.81, 91 cents from Wednesday's closing level.

New York's main contract, light sweet crude for April, eased eight cents to $106.20 a barrel on the back of weak data from Europe and China. It had struck a nine-month high of $106.72 on Wednesday.

"As before, it is the Iran conflict that is causing (Brent) prices to skyrocket," said Commerzbank analyst Carsten Fritsch.

"According to media reports, Japan intends to slash its oil imports from Iran by over 20 percent -- twice as much as previously expected.

"For as long as the oil price continues to rise, Iran is likely to compensate for its reduced sales volume by charging a higher price, and cannot be expected to make any concessions in the nuclear dispute in the near future."

Traders were also on tenterhooks ahead of the latest weekly snapshot of energy inventories in leading global oil consumer the United States.

The oil market had already spiked Tuesday on news that the European Union and Greece finally agreed a second bailout deal, while developments in Iran further boosted prices.

A fruitless visit to Iran by UN nuclear inspectors raised tensions on Wednesday, with Russia warning of "catastrophic" consequences if it leads to a military attack on its Middle East ally.

Washington expressed disappointment, and France said Iran's refusal to let the inspectors in to a key military site was a "missed opportunity" that could undermine chances of reviving wider talks between Tehran and world powers.

But Iran's supreme leader, Ayatollah Ali Khamenei, was defiant and reiterated the assertion that "the Iranian nation has never been seeking an atomic weapon and never will be."

The visit by the team from the International Atomic Energy Agency (IAEA) was aimed at clarifying issues surrounding possible military aspects of Iran's nuclear programme.

"Another day and another $1 per barrel on the price of Brent, reacting to news that the IAEA's attempts to gain access to sites it considers key in Iran's nuclear programme had been thwarted," said PVM analyst David Hufton, in reference to Wednesday's market moves.

The United States and Europe have been ramping up economic sanctions on Iran since November, when the IAEA published a report crystallising -- though not entirely validating -- Western suspicions it was pursuing nuclear weapons research in Parchin and elsewhere.

The measures, targeting vital oil exports, added to four sets of non-economic UN sanctions.

Iran has repeatedly said the embargo would not deter it from its nuclear ambitions, and it has threatened to strike back at any military action, possibly by closing the Strait of Hormuz -- a key export route.

Tehran has also halted the limited amount of oil it exported to Britain and France and threatened to cut supplies to other EU states in retaliation for an EU oil embargo due to come fully into effect in July.

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