LONDON — Russia’s intelligence services targeted high-profile British politicians, civil servants and journalists with cyberespionage and “malicious cyberactivity” as part of sustained attempts to interfere in U.K. political processes, Britain’s government said Thursday.

The Foreign Office said Russia’s FSB agency was responsible for a range of cyberespionage operations in the U.K., including targeting British parliamentarians from multiple parties and “high-profile individuals and entities” from at least 2015, and selectively leaking and amplifying sensitive information to serve Russian interests.

Foreign Office minister Leo Docherty told lawmakers that a cybergroup known as “Star Blizzard,” which British cybersecurity officials believe to be “almost certainly subordinate” to an FSB unit, created false identities to impersonate legitimate contacts and compromise email accounts in the public sector.

“The targeting of this group is not limited to politicians but public-facing figures and institutions of all types. We have seen impersonation and attempts to compromise email accounts in the public sector, universities, media, NGOs and wider civil society,” Docherty said.

Authorities said the group was responsible for the 2018 hacking of the Institute for Statecraft, a U.K. think tank that worked on defending democracy against disinformation, and the leaking of U.S.-U.K. trade documents ahead of the 2019 British general election.

The Foreign Office said that “while some attacks resulted in documents being leaked, attempts to interfere with U.K. politics and democracy have not been successful.”

It said the U.K. on Thursday imposed sanctions on an FSB intelligence officer and a member of Star Blizzard for involvement in the so-called spear-phishing operations. The Russian ambassador to the U.K. has also been summoned, the Foreign Office said.

“Russia’s attempts to interfere in U.K. politics are completely unacceptable and seek to threaten our democratic processes,” Foreign Secretary David Cameron said in a statement. “Despite their repeated efforts, they have failed.”