The Lefortovo court in Moscow on Tuesday extended the detention of Russian-German citizen German Moyzhes, who is accused of treason in a highly secretive case.

Russia has arrested a slew of Western citizens since its full-scale invasion of Ukraine, with Washington accusing Moscow of using them as capital in prisoner exchanges.

What we know about the case

The Russian state-run news agency TASS said migration lawyer Moyzhes, who helped Russians apply for residence permits in Europe, was arrested by Russian security services in Saint Petersburg in May.

The court website states that in a hearing on Tuesday, the pre-trial detention of "G. Moyzhes," charged with treason, had been extended.

No further details were provided, with treason cases — which can carry life sentences — treated as classified in Russia.

It was unclear if the case was connected to Moyzhes' work.

Born in Saint Petersburg, the 39-year-old lawyer grew up partly in Germany but had returned to live and work in his native country.

Moyzhes was working as a lawyer and managing partner for Cologne-based Avers Group Germany. The consultancy provides business support and helps wealthy citizens of post-Soviet countries, including Russia, to gain German residency permits.

Why might Moscow have made the allegations?

Russia is accused of detaining foreign and dual national citizens for use as bargaining chips ahead of prisoner exchanges, with increasing speculation that a major swap between the US and Russia could be in the offing.

A Russian court last week sentenced US journalist Evan Gershkovich to 16 years in prison on espionage charges that Washington has rejected as baseless.

In another secret trial, US-Russian journalist Alsu Kurmasheva was also sentenced to six and a half years in prison for breaking Russia's strict "military censorship" laws.

Russian President Vladimir Putin has indicated that he wants the release of Vadim Krasikov, a Russian who was convicted in Germany of killing a Chechen former rebel commander.

A German court said the killing, in a Berlin park, was an assassination ordered by the Russian state.  The investigative outlet Bellingcat says Krasikov worked for Russia's FSB security service.

rc/fb (AFP, Reuters)