Supporters say an already-imprisoned prominent human rights activist in Iran has been sentenced to 10 years in prison.

Iranian media and officials have not commented on the sentence for Narges Mohammadi, who has campaigned against the death penalty and serves as the vice president of the now-banned Defenders of Human Rights Center in Iran.

A statement from the center said Mohammadi was sentenced on charges including planning crimes to harm the security of Iran, spreading propaganda against the government and forming and managing an illegal group.

Mohammadi can appeal the Revolutionary Court sentence. She's already serving a six-year sentence. The new sentence will extend her time in prison by four years.

Amnesty International said the sentence shows how "Iran's abusive criminal justice system is used as a tool of repression."