Ukraine has published the names and personal details of hundreds of people it claims are Russian agents involved in "criminal activities" in Europe.
The country's military intelligence service revealed details of 620 individuals who it said are registered employees at the Russian Federal Security Services (FSB) headquarters in Moscow.
The list has not been independently verified and the Kremlin did not immediately respond to a request for comment.
If substantiated, the release would represent a huge data breach at the FSB, which has come under fire from Vladimir Putin in recent days.
The Russian president is said to believe the spy agency is partly at fault for the slow progress of the invasion of Ukraine.
Sergey Beseda, head of the FSB’s foreign intelligence branch, was arrested with Anatoly Bolyukh, his deputy, two weeks ago, while the homes of dozens of other officers were also raided.
Andrei Soldatov, an expert on Russian espionage, said that the final reports produced by the FSB on Ukraine in the run-up to the invasion were “simply not right, which is part of the reason as to why things have gone so badly for Russia”.
He added that the service's assessments of popular support among Ukrainians for a Russian invasion and the extent to which the country would resist were “terribly miscalculated”.
"Employees of the FSB of Russia involved in the criminal activities of the aggressor-state in Europe," Ukraine's military intelligence service said in a post on its website, written in Russian.
It provided the names under a photo of the Moscow headquarters of the FSB, a successor to the Soviet-era KGB security police, without sharing further details on the alleged crimes.
It also published what it said were the agents’ places and dates of birth, car number plates and phone numbers.
All 620 agents are registered at the same address: Bolshaya Lubyanka Street in Moscow, the address of FSB, the former KGB. The European countries in which the persons in question are located and work are not specified.
It is the second time in weeks the FSB's security has been potentially compromised.
Earlier this month Ukraine said its intelligence forces were able to intercept a phone call between two agents who were discussing the death of a Russian general.
The Independent has a proud history of campaigning for the rights of the most vulnerable, and we first ran our Refugees Welcome campaign during the war in Syria in 2015. Now, as we renew our campaign and launch this petition in the wake of the unfolding Ukrainian crisis, we are calling on the government to go further and faster to ensure help is delivered. To find out more about our Refugees Welcome campaign, click here. To sign the petition click here. If you would like to donate then please click here for our GoFundMe page.
