A Russian has pleaded not guilty to charges he hacked three US technology companies, potentially compromising personal details of more than 100 million users, including on LinkedIn, after being extradited from the Czech Republic.

Yevgeniy Nikulin, 30, from Moscow, entered his plea in San Francisco’s District Court, after having fought his extradition following his 2016 arrest in Prague.

His case had turned into a battle over whether he should be sent to the United States or Russia, where a Moscow court had in November 2016 issued an arrest warrant for his alleged theft seven years earlier of $3,450 via a site called Webmoney.

The US Department of Justice accused Nikulin of illegally accessing computers belonging to LinkedIn, Dropbox and Formspring in 2012, including by using the credentials of LinkedIn and Formspring employees. LinkedIn, now owned by Microsoft Corp, has said the case was related to a breach that might have compromised information of at least 100 million users.

 “Computer hacking is not just a crime, it is a direct threat to the security and privacy of Americans,” US Attorney General Jeff Sessions said in a statement.

“This is deeply troubling behavior once again emanating from Russia,” he continued. “We will not tolerate criminal cyber-attacks and will make it a priority to investigate and prosecute these crimes, regardless of the country where they originate.”

Nikulin faces nine criminal counts, including causing damage to a protected computer and aggravated identity theft. A federal public defender representing him did not comment. Nikulin has denied wrongdoing in comments to Czech media