Three lawyers who acted for late Russian opposition leader Alexei Navalny have been given jail terms of up to five-and-a-half years on charges of taking part in an "extremist organisation".

Vadim Kobzev, Igor Sergunin and Alexei Liptser were arrested in October 2023 as Russian authorities intensified pressure on the jailed Kremlin critic, who died suddenly last February in an Arctic prison colony.

They were put on trial behind closed doors in Petushki, a town east of Moscow, and accused of "using their status" to relay messages between Navalny and his colleagues.

Navalny had condemned the case as just like Soviet times, and an indication of "the state of rule of law in Russia".

Igor Sergunin was the only one of the three to admit the charge, according to independent reports, and was given a lighter sentence of three-and-a-half years.

Alexei Liptser was jailed for five years in a penal colony and Vadim Kobzev was given five-and-a-half years.

Kobzev's own lawyer, Andrei Grivtsov, said the evidence against them amounted to illegal invasion of privacy.

"They're not allowed to eavesdrop on meetings between a lawyer and a client in a penal colony in principle - there's a direct legislative ban," he told BBC Russian.

Alexei Liptser's lawyer, Andrei Orlov, told reporters that Friday's court decision was very sad: "But we are not going to stop just yet. We are going to keep moving."

The three lawyers were put on trial close to the penal colony in Pokrov, where Navalny was initially sent when he returned to Russia in January 2021, having survived a nerve agent attack that he blamed on Russian leader Vladimir Putin.

The Kremlin denied the allegation and Navalny remained in Russian penal colonies until his death, north of the Arctic Circle and 1,900km (1,200 miles) north-east of Moscow.

His widow, Yulia Navalnaya, blamed Putin for his death, which authorities put down to "sudden death syndrome".

Several months after Navalny was detained in 2021, Navalny's Anti-Corruption Foundation and his regional offices were banned by a Moscow court, which classified them as "extremist".

Navalny, who was already in jail on other charges, was then convicted of founding and funding an extremist organisation too.

The head of Navalny's Anti-Corruption Foundation, Ivan Zhdanov, pointed out that that the three lawyers were sentenced on 17 January - the same day Navalny was arrested and jailed on his return to Russia from Germany: "Tell me this is a coincidence."

Amnesty International said that by targeting lawyers "for merely doing their job, the Russian authorities are dismantling what remains of the right to legal defence".

According to investigators, the three men had acted as members of Navalny's "extremist community", meeting the opposition leader and exchanging information with him.

Yulia Navalnaya said the three men were "political prisoners and should be freed immediately".

Another of Navalny's lawyers, Olga Mikhailova, who has left Russia, said the sentences were "brutal and absurd" and that the men had been punished for honestly carrying out "their duties, their professional and moral position".

Ms Mikhailova, whose offices were raided in 2023, says she herself has also been accused of extremism in absentia. Another Navalny lawyer, Aleksandr Fedulov, also fled Russia after their three colleagues were detained.

After their arrest, Navalny appeared at a court hearing in October 2023 from a maximum security penal colony east of Moscow and complained that he had been denied all legal representation.

"My lawyer is not here. All the other lawyers are not here. Nobody is allowed to visit me. I am isolated and cut off from any information," he told the hearing.

Two months later, he was moved to an even more remote penal colony named Polar Wolf, where he was held in a punishment cell and died aged 47. His widow rejected the cause of death provided by authorities as a lie.