A documentary aired on Russian TV has claimed there was a plot to assassinate ex-Greek Prime Minister Costas Karamanlis over his support for Russian-backed gas pipelines through Greece to Europe.

According to the documentary, which was broadcast on Russia’s TV news show Vesti, in 2009 the country’s FSB security service intercepted a conversation between CIA agentsregarding plans to remove Karamanlis from office – and kill him if necessary.

At least seven terrorist groups were to be involved in the operation, according to the documentary.

Karamanlis, who served from 2004-09 had backed Greece’s participation in the Burgas-Alexandroupoli pipeline and the Southern Stream gas pipeline to Europe.

In September, it was reported that four people will face trial on charges of allegedly plotting to spy on former Greek Prime Minister Costas Karamanlis when he was in office.

A former CIA official named as William Basil has been charged with attempted espionage while two employees of the Greek National Intelligence Service (EYP) face charges of divulging state secrets, the newspaper Kathimerini said

Former PASOK MP and minister Michalis Karchimakis has also been charged with leaking state secrets following an investigation in connection with wiretapping cases and an alleged 2008 plot against Karamanlis, then the head of the New Democracy Conservative party.

The four were said to be trying to keep Karamanlis from bettering relations with Russia over energy pipelines.

Charges were brought against unknown suspects in March 2012 following press reports about a Russian document revealing the plot and came after testimony from Greek secret service agents, police and Karamanlis security guards.

At the time, the Associated Press reported the alleged plot was brought to light by a tip-off from Russia’s spy agency, a court official said.

The official said then-prosecutor Nikos Ornerakis filed a felony count of conspiracy to destabilize the government against “persons unknown” after a preliminary investigation. The probe was sparked by local media reports alleging Russian intelligence services had uncovered a potential plot to topple or assassinate Karamanlis, who served as Prime Minister from 2004 to 2009.

Ioannis Corantis, who headed Greece’s National Intelligence Service at the time, told The Associated Press he was among those called to give evidence in the case, and confirmed that the service had received information from Russia’s spy agency about a suspected plot against Karamanlis. Corantis did not give any details of the alleged plot or speculate who may have been behind it.