The United Nations human rights chief today voiced concern about the fate of human rights defenders in Iran, whose situation she says is becoming increasingly difficult.

Navi Pillay cited in particular the case of Nasrin Sotoudeh, who was on hunger strike for several weeks in Tehran's Evin Prison.

Ms. Sotoudeh, a prominent human rights lawyer involved in defending many high profile cases, was arrested on 4 September and has reportedly been in solitary confinement since then. She is said to have been charged with national security offences.

Following her first court appearance on 15 November, Ms. Sotoudeh reportedly broke the hunger strike she had conducted over a period of several weeks in protest at her detention.

"I am very concerned that Nasrin Sotoudeh's case is part of a much broader crackdown, and that the situation of human rights defenders in Iran is growing more and more difficult," said Ms. Pillay, the UN's High Commissioner for Human Rights. "I urge the Iranian authorities to review her case urgently and expedite her release."

She also cited the cases of several people who are associated with the Centre for Human Rights Defenders founded by Iranian Nobel Laureate Shirin Ebadi and who are currently detained. In addition, several other organizations have had their members arrested or convicted in recent months.

"Freedom of speech and freedom of assembly are enshrined in international law," said Ms. Pillay, "most importantly in the International Covenant on Civil and Political Rights, which is a binding treaty that Iran has ratified."

The Office of the High Commissioner for Human Rights (OHCHR) is scheduled to hold a judicial colloquium from 1 to 2 December in Tehran with more than 30 Iranian judges and prosecutors on issues relating to the right to fair trial and the treatment of detainees.

Ms. Pillay's comments come ahead of Human Rights Day, which is observed annually on 10 December and will this year focus on situations where human rights activists are not free to organize or speak out.

"I encourage the Iranian authorities to open up greater space for human rights lawyers and activists who play a vital and constructive role in protecting human rights in all societies. They may express critical views – but criticism is not a crime."