Iran detained three British military vessels and eight crew members near its boundary with Iraq in the Shatt al Arab waterway on Monday, Iranian state television said. Officials in Tehran alleged that the boats had intruded into Iranian waters.

In London, a spokesman for the Foreign Office confirmed that the Royal Navy had lost contact with three small river patrol vessels early Monday morning in the Shatt al Arab. The British military patrols the southern reaches of Iraq as part of the U.S.-led occupation force, including the waterway that forms part of the border with Iran.

The Islamic Revolutionary Guard Corps, which secures Iran's borders, has repeatedly issued public warnings against violating international boundaries. But Iranian officials have also acknowledged ignoring several violations of the country's airspace by U.S. military aircraft operating in Iraq during the war to depose former president Saddam Hussein, who was a bitter enemy of Iran.

Monday's incident came at a time of strained relations between Tehran and London, leading to speculation that the seizure was intended to remind the coalition that Iran's cooperation on Iraq is not to be taken for granted. British officials said they were seeking to clarify with Iranian authorities the situation of the boats and crew members.

While Britain is the key U.S. partner in Iraq, Iran accuses the British of betraying Iranian trust in a continuing dispute with the International Atomic Energy Agency. Britain was a sponsor of an IAEA resolution Friday in which the U.N. organization said it "deplores" Iran's erratic cooperation with nuclear inspectors.

Government-sponsored demonstrators have gathered outside the British Embassy in downtown Tehran each Friday afternoon for several weeks, chanting slogans and throwing rocks through chancery windows.

The Revolutionary Guard has increased its prominence in Iranian public issues recently. The elite corps, long considered the bastion of hardliners in the conservative forces that dominate the government, abruptly closed Tehran's new international airport early last month, calling a contract with a Turkish firm to operate the facility a security risk and insult to national pride.

"I wouldn't rule anything out," said one diplomat in Tehran, who spoke on condition of anonymity. The guard "has been going through a reactive phase, and the Iranians do have a way of building patterns.

"But it could be what it says it is: It could well be that on a very windy day on the Shatt al Arab, three British boats ended up on the wrong side" of the waterway.

Iranian Foreign Ministry spokesman Hamid Reza Asefi told Iran's main Persian language TV channel that "interrogation of those detained will continue until the matter is clarified," according to the Associated Press.

The British Defense Ministry said the three vessels were being delivered by a Royal Navy training team to the Iraqi Riverine Patrol Service.

Iran's supreme religious leader, Ayatollah Ali Khamenei, on Monday repeated assurances that Iran is not seeking nuclear weapons. Khamenei, who wields ultimate authority under Iran's theocratic system, said both Islam and common sense argue against atomic weapons.

"Iran does not need nuclear arms," Khamenei told an audience of university officials, in remarks quoted by the state news agency IRNA. "Without nuclear arms, Iran has managed to defeat enemies of the nation, including the U.S., in the past."

"The former Soviet Union had stockpiles of nuclear arms," he said, but "it collapsed. The Zionist regime has several hundred warheads, but it has been driven to desperation by the stone-throwing Palestinian campaigners. Nuclear arms cannot work."

Khamenei said Iran would insist on developing atomic power for electricity, despite its vast oil and gas reserves.

"Enemies of the nation are looking for a day when Iranian oil reserves will be depleted and the nation will stretch its hands to them for help," he said. "It is unacceptable."

Correspondent Glenn Frankel in London contributed to this report.

British military boats patrol southern Iraq, including the waterway forming part of Iran border.