A Russian court has sentenced a female member of Jehovah’s Witnesses to six years in prison, a term the group says is the longest a woman has received there since 2017.

The conviction follows a spate of jailings of Witnesses in Russia this month.

Anna Safranova, 56, was convicted of “extremist activities” — the Russian criminal code’s category applied to Jehovah’s Witness activities. She was sentenced Tuesday in a hearing in Astrakhan, a city in the southern part of Russia, according to Jarrod Lopes, a spokesman at the group’s world headquarters in Tuxedo Park, New York.

“The charge brought against me has nothing to do with me,” Ms. Safranova told the court, according to the organization’s report. “I am only a Jehovah’s Witness in my religious affiliation, and that is why I am now on trial. Please forgive me completely.”

Ms. Safranova, a widow, is the primary caretaker for her 81-year-old mother. The group contends its adherents are peaceful and law-abiding, and notes that eight Jehovah’s Witnesses are behind bars in the Astrakhan region.

Altogether, the organization says, there are more than 80 Jehovah’s Witnesses in Russian prisons, the most since the Russian Supreme Court 2017 order that the Witnesses’ legal entities in the nation were to be liquidated.

“Russia’s discriminatory assault on Jehovah’s Witnesses has significantly escalated despite repeated pleas by prominent international human rights bodies to halt the persecution,” Mr. Lopes said.

“Hate is a strong word, but clearly Astrakhan officials have a special animus towards Jehovah’s Witnesses,” he added, pointing out that “another woman, Olga Ivanova, is serving 3½ years in prison, while her husband, Yevgeniy, and two other men are imprisoned for eight years.”

Ms. Ivanova and her husband, Yevgeiny Ivanov, were among four Jehovah’s Witnesses sentenced to lengthy jail terms in October by the Trusovskiy District Court of Astrakhan. The terms handed down were longer than those generally given for crimes such as rape or kidnapping, observers noted at the time.

On Jan. 19, a judge in the Seversk City Court of Russia’s Tomsk Region sentenced Yalchin Badalov, 68, to three years in a penal colony for “engaging in extremist activities,” including peaceful worship and Bible study meetings.

The following day, the same court sentenced Yevgeniy Korotun and Andrey Kolesnichenko to seven- and four-year prison terms, respectively, for their activities as Jehovah’s Witnesses.

“The prison sentences that Russian courts are handing to Jehovah’s Witnesses, for doing nothing more than practicing their faith, are utterly outrageous and unthinkable,” said Rachel Denber, deputy director of the Europe and Central Asia division of Human Rights Watch, an advocacy group. “Prison sentences, even for a single day, for anyone for peaceful worshiping, Bible study, and the like are wrong and violate the fundamental right to freedom of religion for people of any age and any gender.”

Another human rights activist, Denis Krivosheev, deputy director for research at Amnesty International’s Eastern Europe and Central Asia office in London, said the prospects for changing the situation are slight.

Mr. Krivosheev said it was “presently difficult to think of something that would help us make Russia change its ways, but certainly one thing we cannot do is stay silent and ignore such cases.”

He said Amnesty International has long spoken out against the Russian jailings of Jehovah’s Witnesses whose only “crime” is peacefully practicing their faith.

“What it is that makes them hate and persecute Jehovah’s Witnesses? I cannot, I cannot comprehend,” Mr. Krivosheev said. He asserted such prosecutions merely expose the “cruelty and callousness of the authorities that choose to take this path.”

Neither the U.S. Commission on International Religious Freedom nor the State Department provided an immediate response to a request for comment.