Vanunu, who completed an 18-year prison sentence in April for revealing Israeli nuclear secrets to London's Sunday Times newspaper, was re-arrested on Thursday.
As part of his release arrangement, he was barred from meeting with foreigners and discussing his work at Israel's top secret nuclear facility in the Negev desert.
Since his release, Vanunu has met on several occasions with foreign media representatives, but has denied passing on any classified information.
Vanunu's case became a cause celebre when he was kidnapped by Israeli agents in Rome and taken back to Israel for incarceration after he had fled the country.
Israel was widely condemned for the way it treated him, including putting him in solitary confinement for long periods.
Although it is commonly accepted that Israel is a major nuclear power, Israeli authorities refuse to confirm or deny that they have nuclear weapons.