French state services provided by several ministries were targeted in cyberattacks of "unprecedented intensity" according to a statement made by Prime Minister Gabriel Attal's office on Monday.
"Many ministerial services were targeted" from Sunday "using familiar technical means but of unprecedented intensity," Attal's office said, without providing further details of the targets.
A security source told AFP that the attacks "are not currently attributable to Russia," an obvious suspect for many given Paris' support for Kyiv since the invasion of Ukraine.
The PM's staff added that a "crisis cell has been activated to deploy countermeasures", meaning "the impact of these attacks has been reduced for most services and access to state websites restored."
Specialist services including information security agency ANSSI were "implementing filtering measures until the attacks are over."
A group calling itself Anonymous Sudan claimed responsibility for what it said was a distributed denial of service (DDoS) attack on French government network infrastructure.
"We have conducted a massive cyberattack... the damage will be widespread," the group, which posts with an avatar of a hooded Guy Fawkes mask in front of a desert scene with pyramids, said in a Telegram post.
"A lot of different digital government sectors have been affected, including very important websites, with their respective subdomains."
Anonymous Sudan is a known outfit that has carried out attacks in the past year against websites in countries including Sweden, Denmark and Israel.
Purportedly based in Sudan, it says it targets what it deems to be anti-Muslim activity with some signs that it is sympathetic to Russia.
A DDoS attack involves using a computer or network of computers to make a massive number of requests of a target system, overwhelming its ability to respond to legitimate users.
According to U.S. cybersecurity firm Cloudflare, Anonymous Sudan is one of many groups employing DDoS attacks and organizations can protect themselves against its methods.
The latest cyberattack to hit France follows a warning from Attal's defense adviser last week that the Paris Olympics and European Parliament elections this summer could be "significant targets."
Meanwhile, Defense Minister Sebastien Lecornu said last month that protection against "sabotage and cyberattack" by Russia should be stepped up, in an internal note seen by AFP that said his ministry was top of Moscow's target list.