The Israeli former nuclear technician Mordechai Vanunu, released in April after 18 years in jail, has been re-arrested, police say.
Vanunu is widely regarded as a traitor in Israel
He was seized by armed officers and is being held on suspicion of passing on classified information, police say.
Vanunu was convicted of treason over his disclosures about Israel's nuclear weapons programme and jailed in 1986.
Strict conditions were imposed on him after release, including a ban on giving interviews to foreign media.
He has denied passing on classified information since his release, and insists that any information he may have is now nearly 20 years old.
However, Vanunu has repeatedly been in contact with journalists and was interviewed on BBC television just over two weeks ago.
The bishop of the Jerusalem church where Vanunu has lived since his release said he saw him seized by between 30 and 50 men, many armed with machine guns.
Anglican Bishop Riah Abu El-Assal told the BBC News website that Vanunu's room had been searched and his mobile phones, laptop, camera and notebooks seized.
May not leave Israel for a year
Contact with foreigners only by permission
Barred from foreign embassies
Media interviews not permitted
Banned from discussing nuclear secrets
The bishop said some Swedish pilgrims visiting St George's Church had been shocked to tears by the police operation.
"They invaded the cathedral close," he said. "Some of them climbed over the fences, others came through the main gate.
"They terrified, terrorised the guests and the pilgrims, none of whom knew why this invasion happened with machine guns."
The bishop said he was "very angry" at the way Vanunu was seized. He was not allowed to speak to him, but was told he was being taken for interrogation.
Police spokesman Gil Kleiman told the Reuters news agency that Vanunu would be charged at a court hearing on Friday.
There have been suggestions that Vanunu's detention, coming on the day of Yasser Arafat's death, may have been timed to avoid widescale media coverage, says the BBC's Richard Miron in Jerusalem.
Vanunu revealed details of Israel's secret nuclear facilities to a British newspaper in 1986.
Despite Israeli denials, observers declared the country the world's sixth-largest nuclear power.
Before he could reveal more, Vanunu was lured out of hiding in London by a female Israeli secret agent, who persuaded him that she wanted to meet him in Rome.
Once there, Vanunu was overpowered and drugged by other Israeli agents, then shipped back to Israel to be tried in secret.
In an interview after his release, Vanunu said he had acted to prevent a nuclear holocaust.