The leader cyber securityof Germany was fired after allegations that he was too close to Russians.
Arne Schönbohm headed the Federal Cyber Security Authority (BSI) which, since 2016, is in charge of protection of government communications.
German media accused Schönbohm of having ties to people involved with Russian services information.
The Home Office is investigating the allegations against him, but confirmed he had been sacked with immediate effect.
Before leading BSI, Mr Schönbohm had helped set up and run the Cyber Security Council in Germany, a private association that advises businesses and policy makers on themecybersecurity.
He is said to have maintained close links with the club and attended their 10th anniversary celebrations in September.
One of the members of the association was a cyber security company called Protelion, which was found to be a subsidiary of a Russian company allegedly founded by a former KGB member who was honored by President Vladimir Putin.
Protelion was kicked out of the club last weekend, and Germany's Cyber Security Council said claims of links to Russian intelligence were untrue.
A spokesman for Interior Minister Nancy Faeser appeared to confirm that Mr Schönbohm's dismissal came in response to the recent reports, saying:
“The background to this is the allegations that were exposed and widely discussed in the media. The necessary public trust in the neutrality and impartiality of his leadership as chairman of Germany's most important cyber security agency has been damaged."
But they stressed that the security chief will be presumed innocent while the allegations are investigated.
Germany's Der Spiegel reported that Mr Schönbohm had himself requested formal disciplinary proceedings against him, after there was no reaction from the government after the first accusations.
Berlin, on the other hand, appears increasingly concerned that its critical infrastructure could be targeted by Russian intelligence as it steps up its support for Ukraine.
Last week, the Ministry of Defense announced plans to deliver four air defense systems to Kiev. A single IRIS-T unit is said to be capable of defending an entire city from air attack.
