Olympics' most wanted: Terror police fear suspect hunted after Bulgarian bus bomb could be on his way to London 2012

The man is believed to be carrying a U.S. passport under the name of David Jefferson

He is a top target for Israeli security agents who fear their athletes will be attacked by Iranian terror squad

MI5 and Scotland Yard are thought to have raised their threat assessment against the Israeli delegation

Israel fears a repeat of the 1972 Olympic Games when 11 of its athletes and coaches were murdered

Wanted: A terrorist believed to have been involved in a horrific suicide bomb attack in Bulgaria last week has emerged as one of the biggest security threats to the Olympics. A sketch of the man is pictured

A terrorist believed to have been involved in a horrific suicide bomb attack in Bulgaria last week has emerged as one of the biggest security threats to the Olympics.

The man is thought to be carrying a U.S. passport under the name of David Jefferson and fled following the attack which killed six people last Wednesday in the resort of Burgas.

He has emerged as a top target for Israeli security agents who fear their athletes will be attacked by an Iranian terror squad operating in Europe.

The terrorist, who is suspected of helping the suicide bomber, is thought to have another powerful bomb similar to the one which destroyed the Israeli tourist bus.

Following the Israeli concerns, security has been stepped up around its athletes taking part in the Games.

MI5 and Scotland Yard are thought to have raised their threat assessment against the Israeli delegation as Britain prepares for the largest peacetime security operation ahead of the opening of the Olympics this Friday

According to The Sunday Times, the Israeli government - fearing a repeat of the 1972 Olympic Games in Munich when 11 of its athletes and coaches were murdered - has sent agents from its internal security service Shin Bet to increase the protection around its Olympic team.

Israel's external security service Mossad are also thought to have sent a team of agents to Europe to hunt for a group of white Europeans who have converted to Islam and are working with the Iranian Quds force and Hezbollah - the terrorist group backed by Tehran.

Concerns: Security has been stepped up around Israeli athletes taking part in the Olympic Games over fears they could be targeted by an Iranian terror squad operating in Europe. Soldiers are pictured walking past the Olympic Stadium

Security: It is thought MI5 and Scotland Yard have raised their threat assessment against the Israeli delegation

The horrific blast in Bulgaria is thought to be the latest in a number of revenge attacks by Iran because it believes Israel assassinated some of its nuclear scientists. 

Whitehall officials have dismissed the threat of a credible plot against the Israeli Olympic delegation and suggested Israel could be attempting to increase the pressure on British authorities to increase security around the Games.

But a source in the Jewish community in London said: 'There is a pattern emerging with a build-up of attacks against Israelis and Jewish targets by Iran or Hezbollah over the past year. There is a real fear about this.'

The Metropolitan police commissioner Bernard Hogan-Howe suggested last week that extra security measures had been taken to protect Olympic delegations which could be targeted by terrorists.

Worried: The Israeli government fears a repeat of the 1972 Olympic Games in Munich when 11 of its athletes and coaches were murdered. A member of the Arab commandos who seized the Israeli Olympic team quarters at Munich is pictured

Horrific: Armed police are pictured dropping into position on a terrace above the apartments where members of the Israeli Olympic team were held hostage

He said: 'One of the things we have to watch out for is that some of the countries are under threat of terrorism.'

The security operation around the Olympic Games is unprecedented. Protecting the Olympic Park and 26 other venues will be 17,000 troops and 7,000 private security guards. Sniffer dogs and airport-style security screening will also be in place at every entrance to the stadium and snipers will be in place on the roof.

London's streets will also see an extra 12,500 police officers on patrol while the Olympic Stadium has seen panic rooms installed for VIPS and spectators in case of an attack.

Grim: Relatives sit in front of the coffins of people killed in the suicide bombing in the Bulgarian resort of Burgas

Horrific: The burnt tourist bus is seen at Bulgaria's Burgas airport following the suicide attack this week which has raised concerns over security around the Israeli Olympic team