An activist group says a prominent human rights lawyer in Iran who defended women protesting against the Islamic Republic's mandatory headscarf, or hijab, has been convicted and faces years in prison.

The New York-based Center for Human Rights in Iran says Nasrin Sotoudeh, who previously served three years in prison for her work, was convicted in absentia by a Revolutionary Court.

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It remains unclear how many years she'll have to serve. She is currently held at Tehran's Evin prison.

Hadi Ghaemi, the center's executive director, told The Associated Press on Wednesday that Sotoudeh's sentence showed "the insecurity the regime has to any peaceful challenge."

Sotoudeh's conviction was not immediately reported by Iranian state-run media. Iran's mission to the United Nations did not immediately respond to a request for comment.