"As a result of a cyberattack on the France Travail and Cap Emploi services, personal data of applicants was stolen and could be disclosed and used illegally," the service said in a statement on Wednesday.
As many as 43 million users that have registered on the France Travail website over the past 20 years could be affected, the service said. The hackers gained access to users' social security numbers, home addresses and mobile phone numbers, among other things, although not to their banking details, the statement read.
The anti-cybercrime unit of the Paris prosecutor's office has launched an investigation into the incident, France Travail added.
Earlier this week, the Paris prosecutor's office also launched a probe into a massive DDoS-attack against online government services that had taken place from Sunday to Monday and targeted the websites of the French ministries of economy, environment and culture as well as the prime minister's online office and the website of the Directorate General for Civil Aviation. The Anonymous Sudan hacker group claimed responsibility for the attack.