An Israeli court on Tuesday halved a six-month sentence against nuclear whistleblower Mordechai Vanunu, who spent 18 years in jail for divulging Israeli nuclear secrets,

"Considering his ailing health and the absence of indications that his actions put the country's security at risk, we believe his sentence should be reduced," the judges said.

Vanunu, 54, had been sentenced to six months for violating bans on travel and contact with foreign media in 2007, three years after he was released from jail for disclosing the inner workings of Israel's Dimona nuclear plant to Britain's Sunday Times newspaper.

The Jerusalem Magistrates' Court had found him guilty of having contacts with foreign reporters and trying to leave Jerusalem to visit Bethlehem in the Israeli-occupied West Bank.

The 2007 sentence had been suspended pending appeals.

Just before Tuesday's hearing, Vanunu told journalists: "I will talk to you when I'll be free to do so."

Vanunu became an international cause celebre during his time in prison. At home, he is still widely reviled for converting to Christianity shortly before he was kidnapped in Italy and jailed in 1986 after being covertly shipped back to the Jewish state.

Israel is widely believed to be the only nuclear power in the Middle East, with around 200 nuclear warheads, but has a policy of neither confirming nor denying that.

The Jewish state has refused to sign the nuclear Non-Proliferation Treaty or allow international surveillance of Dimona, in the southern Negev desert.