MOSCOW (AFP) - The Russian police on Friday (April 30) detained prominent rights lawyer Ivan Pavlov, who is representing jailed Kremlin critic Alexei Navalny, on criminal charges, his organisation said.

Team 29, of which Mr Pavlov is head, said on its website that the lawyer is facing charges of disclosing information of a preliminary investigation, an offence punishable by up to three months in jail.

It was not immediately clear which case the charges are related to.

"The head of Team 29, Ivan Pavlov, has been detained after a search in Moscow," the organisation wrote.

The Saint Petersburg-based group describes itself as an association of lawyers and journalists fighting for freedom of speech in Russia, where it is known for defending people accused of treason.

The organisation is named after Article 29 of Russia's Constitution, which guarantees freedom of speech, and Chapter 29 of the country's criminal code, which defines crimes against the state including treason and espionage.

Mr Pavlov is defending Navalny's network of regional offices and his Anti-Corruption Foundation after prosecutors moved in April to designate them as extremist, equating them with the Islamic State group and Al-Qaeda and banning them in Russia.

He is also handling the case of former journalist Ivan Safronov, who was arrested in July 2020 on treason charges and is accused of passing state secrets to Czech intelligence.

His pre-trial detention was extended until July 2021 during a court hearing on Friday.

Mr Pavlov's team said that the police also conducted searches on Team 29's Saint Petersburg office and at the home of Mr Pavlov's wife.

His colleague Yevgeny Smirnov said that Mr Pavlov frequently received threats from Russia's Federal Security Service, who allegedly said "we will do everything to put you behind bars".

In an open letter signed by a dozen Russian lawyers, Mr Pavlov's colleagues said they had "no doubt" the arrest was connected to his work.

"We demand an end to the illegal criminal persecution of lawyers," they said in the letter published on the website of Ekho Moskvy radio.

"Criminal cases against human rights defenders and lawyers is the new reality we are entering," opposition movement Open Russia, funded by exiled former oligarch Mikhail Khodorkovsky, wrote on Telegram.