MOSCOW — A Russian military court in Penza convicted seven antifascists of terrorism Monday and sentenced them to prison terms from six to 18 years, in a case widely criticized by human rights groups that claim the defendants were tortured into confessing.

Eleven left-wing antifascists and anarchists were accused by the Federal Security Service (FSB) in 2017 of planning bomb attacks at the 2018 World Cup soccer tournament hosted by Russia and in the lead-up to the 2018 presidential election. Their alleged plan was to destabilize the country and topple the government.

A St. Petersburg military court has not yet handed down its verdict on four of the 11 defendants.

The defendants were accused of organizing a terrorist group called “Network.” They were airsoft enthusiasts, a game similar to paintball. According to the FSB, a successor agency to the KGB, the games were actually a form of training. The organization was banned as a terrorist organization in April.

Several of the defendants have reported torture and threats by FSB investigators. Amnesty International said the men were prosecuted for belonging to a “non-existent ‘terrorist’ organization.”

Those sentenced Monday were Dmitry Pchelintsev, Arman Sagyn­baev, Vasily Kuksov, Mikhail Kulkov, Maxim Ivankin, Andrei Chernov and Ilya Shakursky. Shakursky, Pchelintsev and Kuksov were also accused of arms trafficking.

Pchelintsev, who was accused of being the organizer, got the longest sentence, 18 years.

The Russian human rights organization Memorial said the case against them was fabricated and politically motivated. It has designated them political prisoners.

“We demand their immediate release and that all charges against them for alleged involvement in a terrorist group be dropped,” the group said in a statement in December.

Natalia Prilutskaya, a Russian researcher for Amnesty International, said that the charges were a figment of the Russian security services’ imagination and that the trial was a sham. She said it was clear from the trial that the case was fabricated and that no terrorist organization “Network” ever existed, just a group of young people who liked playing airsoft.

“The main concern about the case was the use of torture in the case of those sentenced today in the Penza case and in the St. Petersburg case where the trial is still going on,” she said in an interview Monday. “Whenever we hear about torture, we have a question about the legitimacy of the evidence.”

“Torture is common in Russia,” she said. “In our work, we get many complaints of torture, especially in cases involving charges of extremism and terrorism.”

She said interviews by Amnesty International with relatives of the defendants indicated that evidence was planted.

Independent newspaper Novaya Gazeta headlined its article on the verdict, “Seven reasons why we do not believe the investigation of the ‘Network’ case,” citing torture, planted or concocted evidence, a changing prosecution case and no evidence of a terrorist plan.

Russian presidential spokesman Dmitry Peskov said Monday that it would be inappropriate for President Vladimir Putin to intervene in the case.

“The president has looked into this situation more than once and repeatedly instructed officials to check everything carefully for compliance with the law,” he said. “Any other intervention in the work of investigative agencies is not possible, particularly on the part of the head of state.”

The FSB arrested a Penza university student, Yegor Zorin, in October 2017 and charged him with participating in a terrorist group. According to authorities, he confessed and implicated others. A day later, Kuksov and Shakursky were arrested, then other members of the group were rounded up.

In January last year, Igor Shishkin, the first one to be sentenced, was given a three-and-a-half-year term, after agreeing to cooperate with investigators in return for leniency.

According to a campaign website set up to defend the rights of the defendants, rupression.com, FSB investigators tortured them by applying electrical wires to their bodies, beating them and hanging them upside down. It alleges agents planted incriminating items, including explosives, weapons and computer files.

Pchelintsev, 27, a vegan shooting instructor interested in environmental issues, said that he and others were anti-authoritarian activists but that there was no formal group or leader, in an interview published Sunday by Novaya Gazeta, where he provided written answers to questions.

“They accused us of ‘planning to plan’ something, but nobody knows exactly what.

“The defendants didn’t know each other. We did not do anything together. Sometimes, very rarely, we went to the same events like concerts, flea markets, sports events or movies. The only thing we had in common was involvement in grass root organizations and that makes the regime mad,” he said.

Another defendant, Viktor Filinkov, a software engineer, whose trial is ongoing, was arrested in January 2018 in St. Petersburg. He was driven in a minivan to the outskirts of the city with his hat pulled down over his face and was tortured for hours until he confessed, he told Mediazone, a Russian online outlet focused on legal rights.

“He shocked my legs and then the handcuffs. Sometimes they punched me in the back and the top of the head. I gave up almost immediately. In the first ten minutes. I was shouting, ‘Tell me what to say, and I will say anything!’ But the violence did not stop,” he said. “Their threats sounded very convincing. I believed that they would act upon them if I didn’t comply.”

Shakursky, 23, described sitting in his underpants, a sock stuffed in his mouth, with wires tied to his big toes.

“They told me to undress, sit on the bench, hands tied with tape and eyes blindfolded. I had the thought that I would never get out alive,” he said in court, while testifying. “They started to shock me, about five times.” He said he confessed to everything the FSB interrogators ordered.

Prilutskaya, the Amnesty International researcher, said the allegations of torture had not been properly investigated.