Veteran Soviet-era rights activist Yelena Bonner, widow of Nobel Peace laureate Andrei Sakharov, has died in the United States at the age of 88.

Bonner died of heart problems Saturday in Boston, where she lived with her son and daughter.

Bonner was a relentless critic of human rights abuses by Soviet-era authorities. She was born in Turkmenistan in 1923 to a Jewish mother and an Armenian father. Her father was executed and her mother sentenced to a labor camp under Soviet leader Josef Stalin.

After a career as a nurse, Bonner married nuclear physicist and fellow dissident Andrei Sakharov in 1972. Both became vocal critics of nuclear weapons proliferation. When the Kremlin banned Sakharov from collecting his 1975 Nobel Peace Prize, Bonner went to Oslo to accept it for him.

In the 1980's, authorities sentenced the couple to internal exile in the city of Gorky for criticizing the Soviet invasion of Afghanistan.

After Sakharov's 1989 death, Bonner remained an outspoken critic of Russian military action in Chechnya and of former Presidents Boris Yeltsin and Vladimir Putin.

The U.S. State Department says it is profoundly saddened at Bonner's death, calling her an extraordinary voice among human rights defenders.

Her family says Bonner will be cremated and her ashes buried in a Moscow cemetery beside Sakharov.