At least six human rights advocates were reported to have been arrested in Iran on Wednesday, dampening hopes that the government was easing its campaign of arrests ahead of the Iranian New Year on March 21.

In another signal of continued government pressure, Fatimeh Karroubi, the wife of the opposition leader Mehdi Karroubi, wrote in a public letter that progovernment forces had demonstrated outside their apartment building in northern Tehran on Sunday, pelting the building with tomatoes and eggs.

The Iranian Committee of Human Rights Reporters reported on its Web site that at least five activists had been arrested in Tehran and one in the southern province of Khuzestan. Another report said that two students, in Shiraz and Kermanshah, were jailed after raids on their homes on Tuesday.

“There was a wave of releases, but there is also a wave of arrests,” said Akbar Atri, a former student leader in Tehran who is now a human rights advocate in Washington. He said that bail figures for those released were large, and suggested that the government was simply solving a problem it created with so many detentions.

“The government is not capable of keeping so many people behind bars,” he said, “and so it is forced to let some of the prisoners out to make space for new ones.”

Mrs. Karroubi wrote in her letter, published on a student Web site, Advarnews, that the demonstrators on Sunday chanted slogans against Mr. Karroubi through loudspeakers and called on the authorities to confront him.