Russia's Kursk region was hit by a “massive” distributed denial-of-service (DDoS) attack on Thursday amid Ukraine’s surprise cross-border incursion, Kursk state officials said in a statement.

The unnamed hackers targeted government and business websites, as well as critical infrastructure services, making some of them temporarily unavailable, state media reported.

Data shared by internet monitoring service NetBlocks shows “sporadic disruptions to internet connectivity in and around Kursk,” likely linked to DDoS attacks targeting local infrastructure.

⚠️ Confirmed: Live network data show sporadic disruptions to internet connectivity in and around Kursk, #Russia, as Ukraine continues its cross-border incursion into Russian territory; the outages are provisionally attributed to DDoS attacks targeting local infrastructure 📉 pic.twitter.com/9LIEA6TY16

— NetBlocks (@netblocks) August 8, 2024

According to Russia’s digital ministry, Kursk online services were hit with over 100,000 junk requests per second at the peak of the attack. DDoS incidents can involve much larger amounts of traffic, sometimes peaking at millions of requests per second.

The internet protocol (IP) addresses involved in the incident were mainly registered in Germany and the U.K., the agency said. DDoS traffic can originate from multiple sources without signifying the exact origin of the attack.

“The attackers’ goal was to disrupt the provision of socially significant services,” the ministry said in a statement. “However, the hackers failed to damage the e-government infrastructure and gain access to user data. All information is reliably protected, and attacks were quickly repelled.”

It is not clear what hacker group is behind the attack. Well-known Ukrainian hacktivist groups, as well as military intelligence services, have not yet claimed responsibility for the incident.

The assault on Kursk is one of Ukraine’s biggest attacks on the bordering Russian region since the start of the full-scale war almost three years ago. Ukraine’s troops reportedly managed to advance up to 15 kilometers into the Kursk region, where authorities have declared a “state of emergency,” calling the situation in the region “very difficult.”

During a briefing on Wednesday, a White House spokesperson declined to comment on whether Ukraine used U.S. assistance in the operation in Kursk but said that the U.S. is going to continue to stay focused on making sure Ukrainians have “what they need to defend themselves against Russia’s aggression.”