Finnish authorities on Thursday blamed a group of Chinese state-sponsored hackers for a breach last year of the Finnish parliament's IT systems.
The Finnish intelligence and security service Supo said the group was known as APT31.
Parliament last year said a number of email accounts linked to lawmakers and employees were hacked, and that this was discovered by parliament's technical surveillance systems.
The speaker of the parliament, Anu Vehvilainen, said the incident was "serious" and that the National Bureau of Investigation (NBI) was continuing its probe.
"When the investigated criminal offences are aggravated espionage, aggravated computer break-in and aggravated message interception everyone understands how serious offences we are dealing with," she said on Thursday.
Neighbouring Norway's parliament reported a similar hack last year. In October, the Norwegian government blamed hackers linked to Russia's military intelligence for that hack.