US authorities say they have broken up an alleged plot to bomb the Israeli and Saudi Arabian embassies in Washington and assassinate the Saudi ambassador to the US.

The alleged plotters were identified as Manssor Arbabsiar and Gholam Shakuri, both originally from Iran, in the criminal complaint unsealed in federal court in New York City.

Mr Arbabsiar, a naturalised US citizen, was arrested in late September. Mr Shakuri is still at large.

"The criminal complaint unsealed today exposes a deadly plot directed by factions of the Iranian government to assassinate a foreign ambassador on US soil with explosives," said Attorney General Eric Holder.

"Through the diligent and coordinated efforts of our law enforcement and intelligence agencies, we were able to disrupt this plot before anyone was harmed. We will continue to investigate this matter vigorously and bring those who have violated any laws to justice."

Mr Holder said the plot was "conceived, sponsored and directed from Iran".

The plot was disrupted by the Federal Bureau of Investigation and Drug Enforcement Administration.

Court documents identified Mr Shakuri as a member of the Quds Force, a branch of the Iranian Islamic Revolutionary Guard Corps.

Mr Shakuri allegedly approved the plan to try to kill the Saudi ambassador during telephone conversations with Mr Arbabsiar, the complaint said.

In July and August, the documents say Arbabsiar paid $100,000 to a DEA informant for the murder of Saudi ambassador Adel Al-Jubeir, court documents said.

Mr Arbabsiar was arrested late last month at New York's John F Kennedy International Airport.

After his arrest, court papers said, Arbabsiar confessed to authorities.

The men are charged with one count of 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 and one count each of conspiracy to use a weapon of mass destruction and conspiracy to commit an act of terrorism.