Yitzhak Yaakov denies the charges

Details of his arrest, on 28 March, only emerged after an Israeli court partially lifted an order restricting reporting of the case.

The British Sunday Times newspaper reported that General Yaakov was believed to have been involved in Israel's nuclear weapons programme.

It added that he was being questioned about his relationship with a Russian woman who may have had access to his work.

BBC Jerusalem correspondent Steven Gibbs says General Yaakov's arrest came as a shock in Israel.

Birthday party

The former brigadier general was arrested last month as he was about to board a flight to Turkey with his Russian girlfriend.

This is not a story of espionage

Yaakov's lawyer

Just days beforehand he had held a lavish 75th birthday party. Amongst the guests were senior Israeli military and defence officials.

In the 1970s he was head of the Israeli defence forces warfare research unit.

The scientist, who holds both Israeli and American citizenship, is charged with handing to a third party confidential information with the intention of harming state security.

Vanunu: Jailed for 18 years for revealing nuclear secrets

Sections of the indictment released to the press said that General Yaakov was warned by security officials not to pass on military information to unauthorised people.

His lawyer emphatically denies that this case is in any way connected with spying.

"This is not a story of espionage, or something that includes an enemy country or enemy agents or a spy who intended on damaging state security," Yehoshua Reznik told Israeli TV.

"The truth will come to light."

Nuclear weapons

Israel has always refused to comment on its nuclear capabilities, but is generally believed to have nuclear weapons.

It maintains what is known as a policy of 'nuclear ambiguity', saying that it will not be the first country to introduce them to the Middle East.

In 1986 Mordechai Vanunu, a former technician, was jailed for 18 years for providing information about the country's Dimona nuclear reactor.

And satellite pictures of the reactor published on the internet last August suggested that the country had enough plutonium to make 200 nuclear weapons.