Tehran, Iran ? The Iranian government imprisons people for expressing their views on a scale unmatched by any other country yet examined, according to the first human rights delegation to visit Iran in seven years.

The five-member United Nations team on Wednesday also criticized Iranian authorities’ use of solitary detention “practiced on a large scale for long periods,” particularly in Tehran’s hillside Evin prison, where many of Iran’s more famous political dissidents are jailed.

“It is the first time the working group has been confronted with such a practice on such a scale,” said Louis Joinet, a French jurist who heads the U.N. Working Group on Arbitrary Detention team that spent 12 days reviewing Iran’s judicial and penal system.

Iran, eager to bolster its sagging economy with foreign business deals, has come under pressure from the West to improve its human rights record.

After the U.N. Human Rights Commission decided in April 2002 to lift its 18-year censure of Iran, officials there agreed to allow human rights investigators to visit.

Joinet declined to say what the group would advise the Islamic republic to do about arbitrary detentions or prison conditions, saying the team would discuss its recommendations with Iranian officials first.

Iran has for years come under fire from international human rights activists for its arrests of political dissidents, closed-door trials, and torture and executions of prisoners.

Tens of thousands of political dissidents have been imprisoned or killed since 1979, when clerics came to power after deposing the late shah.

The clampdown on expression has increased over the past three years. Dozens of newspapers promoting moderate President Mohammed Khatami’s agenda of greater social and political freedom have been closed, and many journalists have been jailed by conservative hard-liners, who control the judiciary.

Other concerns the team raised Wednesday included imprisonment of lawyers who defend political clients, ill-paid and unmotivated state-appointed defense attorneys and excessively high bail for criminal defendants.