Tensions escalate with US and Israel as Tehran accuses the Mossad in fifth murder of scientists

This article is more than 8 years old

This article is more than 8 years old

A chemist working at Iran's main uranium enrichment plant was killed on Wednesday when attackers on a motorbike stuck a magnetic bomb to his car.

The assassination – the fifth against Iranian nuclear scientists in the past two years – is likely to further escalate tensions between Iran and the west.

It took place at 8.30am, at the height of rush-hour in Tehran, according to witnesses quoted in the Iranian media.

A motorcycle pulled up alongside a silver Peugeot 405 carrying the deputy director of the Natanz enrichment plant, Mostafa Ahmadi-Roshan, 32.

The pillion passenger stuck a charge to the door next to the chemist, which detonated as the motorcyclist drove off.

The car's driver was also killed and a pedestrian was wounded, but the charge used appeared to have a sophisticated shape that focused the blast into the car. While the door ended up in nearby trees, much of the car remained intact.

Ahmadi-Roshan was the fifth nuclear scientist to be attacked in Tehran in 24 months. Only one target has survived the daytime attacks, apparently carried out by a well-trained hit team.

Iran has said the US and Israel are behind the assassinations, and blamed the Mossad for Wednesday's killings.

Washington denied any involvement, while Israel, whose military chief had warned Iran on Tuesday to expect more "unnatural" events, declined to comment.

The attacks come at a time of high tension and high stakes in the Gulf. The US has declared it will prohibit the global financing of the Iranian oil trade starting in June in protest at Iran's nuclear programme. The EU is due to decide on its own embargo on Iranian oil later this month.

Iran has reacted by threatening to close the Gulf's narrowest point, the strait of Hormuz – cutting off a fifth of the world's oil supply – if its oil exports are embargoed.

A European diplomat said on Wednesday night that a decision had been taken to impose an oil embargo in six months' time and an embargo on the imports of petrochemical products in three months' time.

This decision will be reviewed in April, in light of its anticipated impact on global oil markets, and then in July, on the eve of it taking effect. The decision will be formally endorsed by EU foreign ministers on January 23.

The Iranian navy has warned the US against deploying an aircraft carrier in the region. The US, with British support, has vowed to keep the oil shipping lanes open and patrol the Gulf as it sees it fit.

Iran has carried out naval exercises in the Gulf and has announced more to come, while Israel and the US are due to carry out their biggest joint war games ever in the next few months.

The oil embargoes are the result of a report by the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), in November citing 'credible' evidence to support longstanding western charges that Iran has experimented with nuclear weapons design. Iran denies any military applications of its nuclear programme.

Iran raised tensions further this week by announcing it had begun enriching uranium at a second plant, a highly-fortified underground site called Fordow, near the holy city of Qom.

Western intelligence agency officials have admitted they are using covert means to try to slow the Iranian programme, including the supply of faulty parts and the Stuxnet computer worm which infected and slowed centrifuges.

Sir John Sawers, the head of MI6, said in a speech in 2010: "We need intelligence-led operations to make it more difficult for countries like Iran to develop nuclear weapons." He added that the intelligence services' role was "to find out what these states are doing … and identify ways to slow down their access to vital materials and technology".

All western intelligence agencies have denied involvement in assassinations.

However, the head of the Israeli Defence Force, Lieutenant General Benny Gantz, predicted on Tuesday that 2012 would be a critical year for Iran which would undergo more "things which take place in an unnatural manner".

Ahmadi-Rohsan was killed in a manner now terrifyingly familiar in Tehran. In November 2010, not far from the scene of Wednesday's assassination, there were two identical attacks involving assailants on motorbikes and magnetic bombs.

One killed Majid Shahriari, a member of the nuclear engineering faculty at Shahid Beheshti University in Tehran who was working on research projects with the Atomic Energy Organization of Iran (AEOI). The other slightly wounded Fereydoun Abbasi-Davani, the subject of UN sanctions and widely suspected in the West of involvement in nuclear weapon design.

In a reflection of his importance in the Iranian programme, Abbasi-Davani was made the head of the AEOI a few months later. The first assassination victim was also a senior figure. Physicist Masoud Ali Mohammadi was killed in January 2010 when a bomb on a parked motorbike exploded as he walked to his car. In what seems unlikely to be a coincidence, Ahmadi-Roshan was killed on the second anniversary of Ali Mohammadi's death.

Last July Darioush Rezaeinejad, an electronics expert, was shot in a Tehran street by gunmen on a motorbike. His affiliation to the nuclear programme has been debated. According to some reports, he worked on high-voltage switches that can be used in nuclear weapons design.

Iranian state agencies described Wednesday's attack as a terrorist operation, and a senior official blamed Israel for it. "The bomb was a magnetic one and the same as the ones previously used for the assassination of the scientists, and is the work of the Zionists," Tehran's deputy governor, Safarali Baratlou, was quoted as saying by the Fars agency. Iran refers to Israel as the Zionist regime.

Iran's vice-president, Mohammad Reza Rahimi, in quotes carried by the state Irna news agency, said: "Iran's enemies should know they cannot prevent Iran's progress by carrying out such terrorist acts."

The AEOI said that Ahmadi-Roshan's death would not deter Iran from its nuclear aspirations. A statement read: "The heinous acts of America and the criminal Zionist regime [Israel] will not disrupt our glorious path and Iran will firmly continue this path with no doubt."

Iran said it was prepared to hold further talks with the international community, represented by a six-nation negotiating group of Britain, the US, Russia, China, France and Germany. However, the office of the EU foreign minister, Lady Ashton, who acts as a point of contact for the group, said it has received no indication from Tehran suggesting any meeting.

IAEA inspectors are due to visit Iran this month to discuss the "possible military dimensions" of the nuclear programme outlined in their November report. Diplomats said the talks' agenda would have to be agreed before the visit went ahead.