FIFTEEN British sailors and marines arrested by Iran’s Revolutionary Guards off the coast of Iraq may be charged with spying.

A website run by associates of Mahmoud Ahmadinejad, the Iranian president, reported last night that the Britons would be put before a court and indicted.

Referring to them as “insurgents”, the site concluded: “If it is proven that they deliberately entered Iranian territory, they will be charged with espionage. If that is proven, they can expect a very serious penalty since according to Iranian law, espionage is one of the most serious offences.”

The warning followed claims by Iranian officials that the British navy personnel had been taken to Tehran, the capital, to explain their “aggressive action” in entering Iranian waters. British officials insist the servicemen were in Iraqi waters when they were held.

The penalty for espionage in Iran is death. However, similar accusations of spying were made when eight British servicemen were detained in the same area in 2004. They were paraded blindfolded on television but did not appear in court and were freed after three nights in detention.

Iranian student groups called yesterday for the 15 detainees to be held until US forces released five Revolutionary Guards captured in Iraq earlier this year.

Al-Sharq al-Awsat, a Saudi-owned newspaper based in London, quoted an Iranian military source as saying that the aim was to trade the Royal Marines and sailors for these Guards.

The claim was backed by other sources in Tehran. “As soon as the corps’s five members are released, the Britons can go home,” said one source close to the Guards.

He said the tactic had been approved by Ayatollah Khamenei, Iran’s supreme leader, who warned last week that Tehran would take “illegal actions” if necessary to maintain its right to develop a nuclear programme.

Iran denounced a tightening of sanctions which the United Nations security council was expected to agree last night in protest at Tehran’s insistence on enriching uranium that could be used for nuclear weapons.

Lord Triesman, the Foreign Office minister, met the Iranian ambassador in London yesterday to demand that consular staff be allowed access to the Britons, one of whom is a woman. His intervention came as a senior Iranian general alleged that the Britons had confessed under interrogation to “aggression into Iran’s waters”.

Intelligence sources said any advance order for the arrests was likely to have come from Major-General Yahya Rahim Safavi, the commander of the Revolutionary Guards.

Subhi Sadek, the Guards’ weekly newspaper, warned last weekend that the force had “the ability to capture a bunch of blue-eyed blond-haired officers and feed them to our fighting cocks”.

Safavi is known to be furious about the recent defections to the West of three senior Guards officers, including a general, and the effect of UN sanctions on his own finances.

A senior Iraqi officer appeared to back Tehran’s claim that the British had entered Iranian waters. “We were informed by Iraqi fishermen after they had returned from sea that there were British gunboats in an area that is out of Iraqi control,” said Brigadier-General Hakim Jassim, who is in charge of Iraq’s territorial waters. “We don’t know why they were there.”

Admiral Sir Alan West, the former head of the Royal Navy, dismissed suggestions that the British boats might have been in Iranian waters. West, who was first sea lord when the previous arrests took place in June 2004, said satellite tracking systems had shown then that the Iranians were lying and the same was certain to be true now.

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