The United States is expressing concern about the arrest of four Iranian student activists who had helped organize pro-reform demonstrations in Tehran. The Iranian government this week banned further protests, which have been staged in support of a reformist scholar who is facing a death sentence.

The State Department says the United States "stands with" Iranians and their quest for freedom and civil liberties, and says authorities in Tehran should know that calls for reform in the country are genuine and come "directly from the hearts of their own citizens."

The comments came in response to the detention in Tehran of four leading student activists in raids by plain-clothes police Tuesday.

Though they were subsequently released without bail, the students face charges of endangering national security. At a news briefing, State Department spokesman Philip Reeker said Iranians are being denied universally recognized free-speech rights.

"The Universal Declaration of Human Rights protects and individual's right to freedom of expression, " he said. "But when Iranian citizens try to exercise this right, and appeal to their government for reform, they're met with violence, with arrests and with death sentences. So we're very concerned about the reports of arrests of student activists, particularly given reported efforts by students to insure their recent demonstrations remained peaceful and lawful."

Mr. Reeker also noted the death sentence still standing against reformist academic Hashem Aghajari, whose prosecution for allegedly insulting Islam touched off what have become Iran's largest public protests in several years.

Even though Iranian supreme leader Ayatollah Ali Khamenei has ordered the judiciary to review the verdict, the crisis around it has not subsided.

Iranian authorities Monday ordered an outright ban on further protests of the Aghajari case, which had been taking on an increasingly political tone and had sparked clashes between reformists and hardline government supporters.

Spokesman Reeker said there has been a broad pattern of arrests of proponents of moderation and pluralism in Iran, and said the "overall deteriorating human rights situation" there continues to give U.S. officials "cause for concern."