Antony Blinken, the US secretary of state, has condemned Russia's arrest of the Wall Street Journal reporter Evan Gershkovich, as Moscow was accused of engaging in "hostage taking" by arresting a high-profile journalist who could be used as leverage in a potential prisoner swap.
"In the strongest possible terms, we condemn the Kremlin's continued attempts to intimidate, repress and punish journalists and civil society voices," Blinken said in a statement.
The White House press secretary, Karine Jean-Pierre, also condemned the arrest and said "These espionage charges are ridiculous. The targeting of American citizens by the Russian government is unacceptable".
Both Blinken and Jean-Pierre advised any US citizens still in Russia to leave immediately.
Gershkovich was detained on Wednesday during a reporting trip to the Urals city of Ekaterinburg. On Thursday, he appeared at the Lefortovo courthouse in Moscow for a brief hearing at which the charges were officially presented. The court ordered him to be held in pre-trial detention until at least 29 May, local media reported.
Russia's FSB security service claimed Gershkovich "was collecting classified information about the activities of one of the enterprises of the Russian military industrial complex". The charges carry a maximum prison sentence of 20 years.
"The Wall Street Journal vehemently denies the allegations from the FSB and seeks the immediate release of our trusted and dedicated reporter, Evan Gershkovich. We stand in solidarity with Evan and his family," the newspaper said in a statement.
Friends and colleagues of Gershkovich called the allegations absurd, describing Gershkovich as a professional and the allegations against him as "ridiculous".
The arrest amounted to "hostage-taking as a tool of statecraft", Russia analyst Mark Galeotti wrote on Twitter.
"It's clear that they've taken a hostage," agreed Ivan Pavlov, Russia's leading defence lawyer in espionage cases, who now lives outside the country. "They've chosen a well-known journalist from an authoritative media outlet. The idea is to have an ace up their sleeve for negotiations."
Pavlov said espionage cases like this could take up to two years from arrest to sentencing, and Gershkovich's only hope of release was either to be included in an exchange or for the current Russian regime to fall.
"Back in 2015, we were sometimes able to get a few people out, but now that has become impossible," he said.
Gershkovich, 31, has lived in Moscow for six years, speaks fluent Russian and is accredited as a journalist with Russia's foreign ministry. Prior to the Wall Street Journal, Gershkovich had worked in Russia for the Moscow Times and Agence France-Presse.
Before his arrest, Gershkovich was reportedly working on a story about Wagner, the notionally private military group run by the businessman Yevgeny Prigozhin, which has done much of the fighting in Ukraine.
Since Vladimir Putin, the Russian president, decided to launch a full-scale invasion of Ukraine last February, reporting from inside Russia has become much more difficult. Russia's foreign ministry has put dozens of journalists on blacklists, barring them from entry, and refused accreditation to others.
A series of laws, including one outlawing "fakes", have made honest reporting on the war from inside Russia difficult and dangerous, and many journalists have left.
However, this is the first time a foreign reporter has been charged with crimes since the beginning of the war.
"It's a signal to foreign journalists that this is it, no more work. The unspoken immunity for accredited journalists does not work any more," said Pavlov.
"Russian journalists heard this signal earlier and almost all of them left. Foreign journalists continued to work, but the times have changed and you can't hope for business as usual any more," he added.
Maria Zakharova, the spokesperson for Russia's foreign ministry, wrote on Telegram on Thursday morning that it was not the first time that journalistic accreditation had been used in Russia as "cover" for other activities.
"What the Wall Street Journal employee was doing in Ekaterinburg had nothing to do with journalism," she wrote.
Dmitry Peskov, Putin's spokesperson, said Gershkovich was "caught red-handed", RIA Novosti reported.
"Peskov's statement is direct evidence that Putin is personally behind this and there will be no civilised way to extract the journalist, only an exchange," wrote political analyst Tatyana Stanovaya.
High-profile arrests of foreigners in Russia often appear to be designed to boost an "exchange pool" of prisoners that Russia can swap for Russians arrested abroad. Last year, Russian authorities arrested the US basketball player Brittney Griner on drugs charges and sentenced her to nine years in prison. She was swapped in December for Viktor Bout, an arms dealer nicknamed the Merchant of Death, who had been held long-term in the US.
Last week, sources said negotiations were under way between western countries and Russia for the possible exchange of two alleged Russian deep-cover spies arrested in Slovenia, but that it had not been possible to reach an agreement. Some observers speculated that bringing espionage charges against Gershkovich could be aimed at improving Russia's negotiating hand to bring these and other prisoners back to Russia.
