Lyudmila Alexeyeva, a Soviet-era dissident who became a symbol of resistance in modern-day Russia, has died at the age of 91 after a long illness.

In a career emblematic of the country’s turbulent history, she defended human rights in the Soviet Union from the 1950s, and continued to do so in Vladimir Putin’s Russia.

Mikhail Fedotov, head of the Kremlin Human Rights Council, said Alexeyeva died on Saturday in a Moscow hospital.

“This is a huge loss for the entire human rights movement in Russia,” Fedotov said.

“She had been struggling with illness recently, but her mind was always stronger than her body and far stronger than any disease.”

Lyudmila Alexeyeva receives a human rights award from Russian president Vladimir Putin in 2017. Photograph: Yuri Kochetkov/AP

Alexeyeva had been the chair of the Moscow Helsinki Group, one of Russia’s oldest human rights organisations, which she helped found in 1976. The group lamented the loss of a “legendary, wise and humane person who remained a defender of human rights until the last moments of her life”.

Alexeyeva trained as an archaeologist and in the late 1950s, her apartment became a meeting place for the Soviet dissident intelligentsia, and a point for storing and distributing banned publications.

She campaigned against trials for dissidents, losing her job as a science publisher and enduring numerous searches and interrogations by the KGB. With her security under threat, she left the USSR in 1977 for the United States.

Alexeyeva returned to Russia in 1993 after the Soviet Union collapsed, and became a strong critic of Putin.

Lyudmila Alexeyeva protesting in 2009 with a banner that reads ‘Respect the Constitution’. Photograph: Alexey Sazonov/AFP/Getty Images

She criticised Moscow’s seizure of the Crimea peninsula from Ukraine in 2014 for “bringing shame on my country”. The following year, she denounced the “awful political killing” of the opposition leader Boris Nemtsov.

She also tried to shed light on the fate of accountant Sergei Magnitsky, who died in prison after accusing Russian officials of tax fraud, and denounced the imprisonment of anti-Kremlin tycoon Mikhail Khodorkovsky.

Kremlin spokesman Dmitry Peskov said Putin had sent a message of condolences to her family. The president “greatly appreciates Lyudmila Alexeyeva’s contribution to the development of civil society in Russia and had great respect for her point of view on several issues concerning the life of the country”, Peskov said.

In 2009, the European parliament awarded Alexeyeva the prestigious Sakharov prize for defenders of human thought, along with the Memorial human rights group.

“If I save even one person, it’s already a true joy,” she said at the time.