US accuses Iran of bomb plot to kill Saudi ambassador in Washington

The US has accused Iran of a "flagrant" violation of international law after claiming the government in Tehran was involved in a plan to assassinate Saudi Arabia's ambassador to Washington in what officials called a "deadly murder plot".

At a press conference, Eric Holder, the Attorney General, described the alleged conspiracy to detonate a bomb in a restaurant frequented by the diplomat, Adel al-Jubeir. Had it succeeded, scores of bystanders could also have been killed. Two men, including a member of Iran's special-forces unit, the Quds, were charged with orchestrating the plot. One of the duo, Manssor Arbabsiar, has been arrested and appeared in New York Federal court last night, wearing blue jeans and a dress shirt. The other, Gholam Shakuri, is still at large.

The allegations will dramatically ratchet-up tension between the US and Tehran. They represent the first time in recent history that the country, a member of the so-called "Axis of Evil", has been accused of sponsoring attempted terrorist activity on US soil.

Washington immediately announced economic sanctions against five Iranian individuals connected to the affair. "In addition to holding these individual conspirators accountable for their alleged role in this plot, the United States is committed to holding Iran accountable for its actions," said Holder. The news also sent an immediate diplomatic shockwave through the Middle East. King Abdullah, the Saudi monarch, was informed of the plot two weeks ago, and officials in Riyadh predicted that they would send Iranian-Saudi relations to "their lowest point yet".

Iran's mission to the United Nations responded by denying any involvement in the alleged bomb conspiracy "We categorically reject these baseless allegations," it said.

Details of the supposed plot, and how it was uncovered, were still emerging late last night. Robert Meuller, the FBI director who appeared alongside Holder at the press conference, said the case "reads like the pages of a Hollywood script". Documents lodged in court say that it unwound because of an alleged drug smuggler who was arrested earlier this year and, in order to avoid incarceration, had agreed to act as an informant for the Drugs Enforcement Administration.

The unnamed informant posed as a member of the Zetas drug cartel and agreed to meet with Arbabsiar and Shakuri in Mexico in May. Subsequent meetings took place in the US over the coming months, And further details of were hashed-out over the telephone.

Arbabsiar, a 56-year-old naturalised US citizen, outlined the specifics of his plot during a meeting in July. He apparently told the informant that he wanted Mexican drug cartel members to carry out attacks on the Israeli and Saudi embassies, as well as seeking to assassinate al-Jubeir. Hiring Latino assassins would prevent the operation from being traced back to Tehran. He added that the planned strikes had been authorised by his superiors, who were relaxed about the prospect of them causing "mass casualties".

"They want that guy [the Ambassador] done [killed]," Arbabsiar is alleged to have said during one conversation. When told that bombing the Saudi's favourite restaurant could potentially kill US congressmen who also regularly dined there, he replied "no big deal".

The informant negotiated a fee of $1.5m for the operation. On 29 September, shortly after he had received a down-payment of $100,000, Arbabsiar was arrested at New York's JFK Airport as he travelled to Mexico to finalise details of the plan.

Holder stressed no explosives were ever acquired for the plot, meaning that the public were never in danger.

Arbabsiar and Shakuri are charged with "conspiracy to murder a foreign official," two counts of "foreign travel and use of interstate and foreign commerce facilities in the commission of murder for hire," as well as "conspiracy to use a weapon of mass destruction" and "conspiracy to commit an act of terrorism. If convicted, they face life in prison.