Mousavi, who has said he is being increasingly isolated, lost his main link to the world after his official Web site, Kalemeh, came up blank and stripped of any text or pictures. Mousavi's associate Ali Reza Beheshti told The Associated Press the site had been taken down by unknown hackers.

In a message on the site late Thursday, Mousavi had said he would seek permission for future protests, even though he said unfair restrictions were being imposed. He said he has been asked by the Interior Ministry to apply in person, a week ahead of time.

The opposition leader noted that Ahmadinejad has been able to hold two postelection marches and a Tehran rally "that were well-publicized on state television, seeming to encourage participation with their regularly advertised march routes."

Mousavi has said the authorities are pressuring him to withdraw his challenge by trying to isolate and discredit him. He hasn't led a rally in more than a week.

Khamenei has ordered a large security detail around Mousavi — ostensibly to protect him, but presumably also to restrict his movements. Authorities have also targeted those close to Mousavi.

Late Thursday, state TV reported that the head of Mousavi's information committee, Abolfazl Fateh, was banned from leaving Iran for Britain. The report, which could not be verified independently, identified Fateh as a doctoral student in Britain.

The semiofficial Fars news agency said Fateh was banned from travel so authorities could investigate "some of the recent gatherings," a reference to election protests.

At least 11 Mousavi campaign workers and 25 staffers on his newspaper have been detained.

On Wednesday, 70 university professors were detained immediately after meeting with Mousavi. All but four have been released. Those still in custody included Qorban Behzadiannejad, Mousavi's former campaign manager.

At least 17 people have been killed in postelection protests, in addition to eight members of the Basij, the government has said.

Laub reported from Cairo; Associated Press writers Shaya Tayefe Mohajer in Cairo and Ben Feller in Washington contributed to this report.