In a report published on Friday, Alphabet's Mandiant cyber unit said it had caught the hacking group known as APT29, which is alleged by Western intelligence to act on behalf of Russia's SVR foreign spy agency, trying to trick "key German political figures" into opening an email masquerading as an invitation to a dinner event hosted by the Christian Democratic Union, Germany's center-right political party.

An alert circulated by Germany's BSI cyber agency and reviewed by Reuters referred to the same incident, saying that state-backed cyber spies were targeting German political parties in an effort to build long-term access and exfiltrate data.

The alert did not give further details on who was believed to be responsible and neither it nor Mandiant provided details on who specifically was targeted. The BSI did not immediately return a request for comment.

The Russian embassy in Washington also did not immediately respond to an email requesting comment.

The alleged intrusion effort occurred one year after Germany expelled 50 Russian diplomats to reportedly "reduce the presence of Russian intelligence in Germany."

Relations between the two countries have remained largely frozen, Russian President Vladimir Putin said in December. Germany is among the Western nations that have provided military support for Ukraine in its war with Russia.

Germany's Der Spiegel first reported on the alleged hacking campaign earlier on Friday.

(Reporting by Christopher Bing and Raphael Satter; Editing by Chizu Nomiyama and Paul Simao)