Veteran Soviet-era rights activist Yelena Bonner, the 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 had lived in recent years with her son and daughter as her health deteriorated. She had previously suffered two heart attacks. Family members say Bonner's remains will be cremated and her ashes will be interred in a Moscow cemetery beside Sakharov, who died in 1989.

Bonner was a relentless critic of human rights abuses by Soviet-era authorities. She met Sakharov, a fellow dissident, in 1970 and married him two years later.

Sakharov was a nuclear physicist who helped to develop the Soviet atomic bomb but later campaigned against nuclear proliferation and won the Nobel Peace Prize for his activism in 1975. Soviet authorities barred him from collecting the award and Bonner traveled to Oslo to accept it on his behalf.

Soviet authorities sent Sakharov into internal exile in the western city of Gorky, now known as Nizhny Novgorod, in 1980 for criticizing the Soviet invasion of Afghanistan. The government later sentenced Bonner to internal exile in Gorky in 1984.

The two lived together in an apartment under constant surveillance until Soviet leader Mikhail Gorbachev allowed them to return to Moscow in 1986 as part of his Perestroika, or reform policy.

After Sakharov's death and the 1991 fall of the Soviet Union, Bonner served as a member of Russia's human rights commission under its first post-Soviet president, Boris Yeltsin. But, she later quit the panel in protest over Mr. Yeltsin's decision to send troops to Chechnya to fight separatists in the Caucasus region.

In her final years, she spent increasingly long periods with her family in Boston, where she frequently criticized the rights record of Russian leader Vladimir Putin. The former KGB officer restored many of the Soviet-era powers of the Russian security forces after taking office as president in 2000. He has been serving as prime minister since 2008.

Bonner signed a petition last year calling on Mr. Putin to step down.

Bonner was born in Soviet Turkmenistan in 1923 to a Jewish mother and an Armenian father who were persecuted under Soviet leader Josef Stalin. Her father, a leading Communist party intellectual, was executed in 1938, and her mother was sent to a labor camp for years. After high school, Bonner served as a Soviet nurse in World War Two.