PARIS • France has accused Iran's intelligence ministry of being behind a foiled plot to bomb an exiled opposition group near the French capital in a move that risks straining already complicated ties between Paris and Teheran.

The French government announced on Tuesday that it was freezing assets belonging to two suspected Iranian intelligence operatives, as well as others belonging to Iran's ministry of intelligence and security.

France's decision to take retaliatory measures and go public with the accusations was taken three months after the alleged plot to bomb a meeting of the People's Mujahedeen of Iran (MEK) in a suburb of Paris.

"This extremely serious act envisaged on our territory could not go without a response," France's interior, foreign and economy ministers said in a rare joint statement. "In taking this decision, France underlines its determination to fight against terrorism in all its forms, particularly on its own territory."

A French diplomatic source told AFP that the security forces had concluded that "the head of operations at the (Iranian) intelligence ministry ordered it". Iran immediately denied any involvement, as it did in July when the MEK accused it of being responsible.

Iranian foreign ministry spokesman Bahram Ghasemi told AFP in an interview that Teheran rejected the French complaint "completely and forcefully", but said the door for discussion was open.

"If there is a misunderstanding... about a thing that does not exist, be it a conspiracy by others or a mistake, we can sit down and talk about it," he said on Tuesday.

The US, which has been intensifying pressure on Iran, warned that "this outrageous behaviour will not be tolerated" in a tweet from the White House's National Security Council.

The alleged bomb plot came to light two days after thousands of Iranian opposition supporters gathered at an exhibition centre outside Paris on June 30. The meeting was attended by two allies of US President Donald Trump, former House Speaker Newt Gingrich and former New York mayor Rudy Giuliani.

The MEK was formed in the 1960s to overthrow the Shah of Iran and it continues to organise opposition to the current leaders of the Islamic Republic who took power following the 1979 revolution.

Belgium announced in July that it had arrested a couple in a Brussels suburb who were suspected of preparing to drive a car packed with explosives to the French rally.

A total of six people were then detained in coordinated raids by European police, including an Iranian diplomat based in Vienna.

The diplomat, Mr Assadollah Asadi, was targeted by the asset freezes announced by the French authorities on Tuesday, along with Mr Saeid Hashemi Moghadam, who the French diplomatic source said was head of operations at the intelligence ministry.

The measures announced on Tuesday come as French President Emmanuel Macron and his Iranian counterpart Hassan Rouhani are at odds over a host of issues.

Mr Macron, who hoped to improve ties with Teheran at the start of his presidency last year, has allied with Iran over the 2015 nuclear deal which limits the Islamic Republic's atomic programme.

While Mr Trump has pulled the US out of the agreement and denounced it, Mr Macron has been a vocal supporter and has worked to keep the accord alive despite American sanctions.

But Mr Macron is at loggerheads with Mr Rouhani over the wars in Syria and Yemen, in which Iran is a major player, and has also raised concerns about the country's ballistic missile programme.

AGENCE FRANCE-PRESSE