Four Iranian nationals have been charged with plotting to kidnap a New York-based journalist, the US Department of Justice says.

The indictment did not name the target, but Masih Alinejad, an Iranian-born author, says it was her.

The conspirators, described as intelligence officials, also allegedly plotted to lure a person in the UK and three others in Canada to Iran.

All of the targets had been critical of Iran, says the Manhattan indictment.

Prosecutors said the Iranian government had sought to lure the New York-based journalist to a third country where the abduction was planned.

The plotters even offered money to the writer's relatives in Iran to betray the target, which they refused to do, the indictment contends.

The defendants are believed to be based in Iran, authorities said.

The plotters hired private investigators to spy on the target's Brooklyn home and family, and set up a high-definition live video feed of the property, according to the indictment.

The kidnap conspirators also researched a service offering military-style speedboats for evacuation from New York City, and maritime routes to Venezuela, an Iranian ally.

Ms Alinejad, 44, runs My Stealthy Freedom, which campaigns against mandatory wearing of the veil for Iranian women.

She told the New York Times that the plot showed the Iranian authorities were "scared" of her, "Otherwise, they would not send anyone here to kidnap me."

US authorities said the kidnappers were aided by a fifth defendant, California resident Niloufar Bahadorifar, who was arrested on 1 July.

She is not accused herself of participating directly in the plot, but is charged with providing financial aid to the conspirators and violating sanctions against Iran.

Ms Bahadorifar has pleaded not guilty and been released on bail, authorities said.

The justice department also said the defendants are charged with fraud, money laundering and sanctions violations.

"As alleged, four of the defendants monitored and planned to kidnap a US citizen of Iranian origin who has been critical of the regime's autocracy, and to forcibly take their intended victim to Iran," said federal prosecutor Audrey Strauss for the Southern District of New York.

William Sweeney, the head of New York's FBI office, said it sounded a bit like "some far-fetched movie plot".

"We allege a group, backed by the Iranian government, conspired to kidnap a US-based journalist here on our soil and forcibly return her to Iran," he said. "Not on our watch." (Text, excluding headline from BBC')

Update news