GENEVA - Iran is cracking down on activists and their lawyers, meting out harsh sentences in an effort to quash pro-democracy activities, United Nations human rights experts said on Friday.

In a joint statement, the independent experts called for the immediate release of human rights defenders including Narges Mohammadi, whom they said was rearrested on April 21 to serve a six-year prison sentence handed down by an appeals court.

"The conviction and extremely harsh sentencing of human rights defenders is an indication of mounting repression against the legitimate activities of human rights defenders and represents a serious setback for the protection of human rights in Iran," said Ahmed Shaheed, UN special rapporteur on Iran.

Thousands of opposition supporters have been detained since the disputed 2009 presidential election won by President Mahmoud Ahmadinejad, including scores of senior reformist figures.

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