LONDON- Britain on Wednesday accused Iran's elite Revolutionary Guard of supplying explosives technology to insurgents in Iraq who have killed several British soldiers in a wave of attacks this year.
There is also evidence that Tehran's ideological army was in contact with Sunni Muslim rebel groups fighting foreign forces in Iraq, a senior British official in London told reporters on condition of anonymity.
The comments came as Britain's embassy in Tehran angrily denied claims in the Iranian press that it was stirring up unrest in the oil-rich southwest of the Islamic republic, just across the border from where British soldiers are based in Iraq.
Iran's foreign ministry spokesman Hamid Reza Assefi dismissed what he called the British "lies" and called for proof.
"If they have proof, they only have to provide it," he said, quoted by the local media. "But they have no proof. They (the British) are the ones to blame for the instability in Iraq, and they accuse others."
The spokesman said Iraqi officials had acknowledged the "positive and constructive policies of Iran in Iraq".
London has previously hinted at an Iranian link with the insurgency in neighbouring Iraq, but Wednesday brought the first specific accusation.
The British official said the Iranian action could be an attempt to warn off London over its demands that Tehran abandon its controversial nuclear programme.
"It would be entirely natural that they would want to send a message: 'Don't mess with us,'" he said.
Britain believed the Revolutionary Guards had been responsible for supplying the explosives technology -- the specifics of which the official did not detail -- used in a series of deadly attacks on British troops earlier this year.
Eight British soldiers were killed over the summer.
"We think it has come from Lebanese Hezbollah via Iran," the official said, refusing to say whether Britain believed the actions were on the orders of the government in Tehran.
In August, a US intelligence official said anonymously that Washington believed a cache of manufactured bombs seized in Iraq had been smuggled into the country by the Revolutionary Guard.
Although Iran is Shia Muslim, the official said it now appeared elements from the country were in contact with Sunni insurgent groups.
"There is some evidence that the Iranians are in contact with Sunni groups. I don't think it is for a benign purpose," the official said.
"If part of the aim was to tie down the coalition in Iraq, it would be entirely consistent with supporting those groups."
London had protested to Tehran, which had denied responsibility, the official added.
Britain has around 8,000 troops in Iraq, mainly based in the south of the country. Since the March 2003 invasion of the country, 95 British military personnel in Iraq have died as a result of combat, accident or natural causes.
In further friction, Britain's embassy in Tehran issued a furious response Wednesday to a string of reports in the hardline Iranian press alleging that British operatives based in southern Iraq were involved in a series of bombings in Khuzestan province prior to Iran's presidential elections in June.
"Recent reporting in Iran alleging UK involvement in the explosions and unrest in Khuzestan has ceased to be objective and professional reporting of the facts," it said in a statement.
"Instead some papers have been publishing unfounded fantasy. They claim to have evidence, derived from ambiguously named sources, but so far evidence has not been put forward for these allegations," the embassy said.
Last year Iran held the crews of three Royal Marine river patrol boats from Iraq for three days, charging the vessels had strayed on to the Iranian side of the Shatt al-Arab waterway which divides the two countries.
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