Russian police arrested the editor of the investigative website that uncovered the identity of the perpetrators of the Salisbury poisonings in the latest round of a sustained crackdown on independent media. 

Roman Dobrokhotov, the editor of Insider, a Russian-language website, was detained during a raid on his Moscow flat early on Wednesday morning. He was released in the evening. 

"Looks like a raid. Police are knocking," he tweeted on Wednesday morning. His wife reported the raids to the OVD-Info legal aid group. Both phones became unavailable shortly afterwards. 

Pravozashchita Otkrytki, a legal aid group, said police seized mobile phones, laptops and tablets during the raid, as well as Mr Dobrokhotov’s international passport. 

Russian state media reported that Mr Dobrokhotov had been detained in connection with a defamation complaint brought by a Dutch blogger called Maxim van der Werff.

Mr van der Werff’s Russian lawyer told RIA Novosti that a criminal complaint filed with Russian police related to an Insider article that claimed the Russian ministry of defence used her client to distribute disinformation about the shooting down of Malaysian Airlines flight MH17 over Ukraine in 2014.

Mr Dobrokhotov’s arrest came hours before he was due to fly out of the country, said Sergei Yezhov, a journalist at the Insider.

A week earlier Russian authorities designated the Insider, which is registered in Latvia, as a "foreign agent".

The label subjects outlets to additional scrutiny from the authorities and compels them to preface all publications with a disclaimer. It also carries significant stigma that can make it difficult to continue operate.  

Several independent media outlets have been handed the designation in recent months in an apparently systematic crackdown on critical media ahead of parliamentary elections in September.  

Recent designations include Open Media, Radio Svoboda, and Proekt Media journalists.

Meduza, a Latvia-based Russian news outlet, appealed for crowd funding after being listed as a foreign agent earlier this year, saying the designation had scared away advertisers.

The Insider specialises in investigations into the Russian intelligence community. It partnered with the British investigative group Bellingcat for a series of high-profile investigations into the poisonings of the former spy Sergei Skripal and opposition leader Alexei Navalny, including the scoops on the identities of Mr Skripal’s purported attackers.

Earlier this week, Russian authorities blocked about 50 websites linked to Mr Navalny, who is currently in prison.