The daughter of a prominent Iranian human rights lawyer says her father has started a hunger strike to protest the conditions of his imprisonment.

Maede Soltani, who lives in Germany, said Abdolfattah Soltani stopped eating on his 60th birthday on Saturday, to protest the lack of medical care for himself and other dissidents jailed in Tehran's infamous Evin prison.

Soltani co-founded a human rights group with Iranian Nobel Peace Prize laureate Shirin Ebadi. He was arrested in 2011 and later sentenced to 13 years in prison on various charges, including co-founding the Center for Human Rights Defenders and endangering national security.

Maede Soltani said Sunday three other inmates have joined her father's hunger strike, refusing to eat and drinking only tea or water, "putting their life in jeopardy."