"Vanunu was arrested (for) a relationship between a man and a woman, with a Norwegian citizen," attorney Avigdor Feldman told reporters.

"He is not being accused of giving any secrets. She is not interested in nuclear business -- she's interested in Mordechai Vanunu (and he) is probably interested in her," Feldman said.

A Jerusalem court ordered Vanunu, who was taken into police custody on Monday, put under house arrest for three days pending an indictment, police said.

Vanunu was jailed as a traitor in 1986 and served an 18-year sentence after discussing his work as a technician at Israel's Dimona nuclear reactor with a British newspaper, an interview that led experts to conclude the facility had produced fissile material for as many as 200 atomic warheads.

After his release from jail in 2004, Israeli defense authorities barred Vanunu from traveling abroad or speaking with foreigners, alleging he has more details on the Dimona atomic reactor to divulge.

The restrictions, upheld by Israel's Supreme Court, have been condemned by international human rights groups.

Vanunu denies he poses a security risk but says he will pursue anti-nuclear activities and wants to live abroad.

In court on Tuesday, Vanunu -- who refuses in protest against Israel to speak Hebrew publicly -- addressed reporters in English.

"This Jewish state has 200 atomic ... hydrogen bombs, atomic weapons, neutron bomb," he said. "They are not able to say they have the bomb, they are not able to destroy anyone ... instead they arrest Vanunu Mordechai."

Israel neither confirms nor denies having the Middle East's only atomic weapons under a policy of "strategic ambiguity" billed as warding off enemies while avoiding arms races.

Vanunu, a Jewish convert to Christianity, argues that by refusing international inspections at Dimona, Israel inflames regional tensions and risks a "second Holocaust."

He has also said the Jewish state has no right to exist, and there has been little public sympathy for him in Israel.

In 2007, Vanunu was sentenced to six months in jail for violating the ban on contact with foreigners.

Reuters