The Czech Republic said on Friday it had handed over a Russian hacker to the US, where he was being searched for alleged cyberattacks in social networks.
Yevgeniy Nikulin, who is also being sought for fraud in his native Russia, has been in a joint operation with the FBI since his arrest in the Czech capital in 2016 in a Prague jail
The case comes under accusations from Washington, Russia is trying to "meddle" in hacker attacks on the US election won by Donald Trump in 2016, charges dismissed by the Kremlin.
The Czech Ministry of Justice "confirms the extradition of the Russian citizen Y. Nikulin to the United States" Ministry spokeswoman Tereza Shejbalova said on Twitter.
The extradition "took place overnight," she added.
The 30-year-old Moscow man appeared on Friday in front of a federal judge in San Francisco, according to the US Department of Justice.
"This is deeply troubling behavior emanating from Russia again," said US Attorney General Jeff Sessions in a press release.
"Computer hacking is not only a crime, but a direct threat to the security and privacy of Americans."
Nikulin charges include computer intrusion and identity theft, and carry penalties of more than a decade in jail and a million dollars in fines according to prosecutors.
Following Nikulin's arrest, Moscow accused Washington of harassing and praising its citizens
He then issued a separate arrest warrant for alleged theft from the WebMoney settlement system.
The US has accused Nikulin of plunging into social networks LinkedIn and Formspring The filehosting service Dropbox said Nikulin's lawyer Martin Sadilek at the time AFP
He also said that Nikulin claims that FBI investigators have twice attempted to persuade him to confess to cyber attacks on the US Democratic Party. 1
In Russia, Senator Igor Morozov has accused Prague and told the Ria Novosti news agency that Moscow will demand "its return to our country, and it is up to the Russian judiciary to decide whether Nikulin violated or punished the law."  "It is time to stop this law of the American jungle," added the Senator, who reports on international affairs.
Alexey Kolmakov, Spokesman for the Russian Embassy in Prague, said that the Czech Republic, a member of the EU and NATO, "once again preferred his notorious solidarity with his American ally."