Moscow has told the US embassy to “mind your own business” after Washington’s diplomatic mission raised concerns about curbs on media freedom in Russia.

Rebecca Ross, the spokeswoman for the US embassy, on Tuesday expressed concern about a clampdown on journalists in Russia.

“Watching arrest after arrest of Russian journalists – it’s starting to look like a concerted campaign against #MediaFreedom,” she tweeted.

“Mind your own business,” the Russian foreign ministry tweeted in response late on Tuesday.

Earlier that day the FSB security agency, the successor to the Soviet-era KGB, arrested a respected former journalist, Ivan Safronov, 30, on suspicion of state treason.

His detention sparked uproar among supporters and journalists who say his arrest is punishment for his coverage of Russia’s defence sector.

A member of Safronov’s defence team, Yevgeny Smirnov, said the former journalist, who used to work for Kommersant and Vedomosti newspapers, is suspected of cooperating with Czech intelligence since 2012.

The FSB investigators believe that the Czech intelligence acts under the guidance of the US, Smirnov said.

The FSB claims Safronov collected confidential data about the Russian military, defence, and security, and handed it over to the intelligence of a NATO member country.

On Wednesday, Kremlin spokesman Dmitry Peskov insisted again that Safronov’s arrest was not related to his work as a journalist.