Local authorities in Crimea are warning of internet disruptions from distributed denial-of-service (DDoS) attacks targeting telecommunication providers.

The “massive” DDoS attacks, which overwhelm targeted networks with a flood of junk internet traffic, were launched against Crimean telecom companies on Wednesday and are still ongoing, according to Crimean officials.

“Work is underway to repel attacks. There may be interruptions in providing internet services,” said Oleg Kryuchkov, the advisor to the Crimea region, which has been occupied by Russian forces since 2014.

In Crimea’s largest city, Sevastopol, the attackers mostly targeted local internet provider Miranda Media, which is connected to Russian national telecom provider Rostelecom. Miranda Media was sanctioned by the European Union in 2023 for providing services to illegal authorities and institutions in Crimea in the interests of Russia.

Several local subscribers complained on the company’s Telegram channel that their internet connection has been “terrible” for the past two days, but Miranda Media hasn’t released an official statement about the disruptions. The company did not respond to a request for comment.

“The enemy attacks this particular operator for a reason,” a spokesperson for Sevastopol’s government said on Telegram. Miranda Media provides “core communication channels” for the city’s emergency call center, they added.

The attack temporarily disrupted the call center’s operations, but local authorities announced on Thursday that they have restored its functionality.

Ukraine’s military intelligence (HUR) claimed responsibility on Wednesday for the cyberattacks on “several of Russia’s largest internet providers” operating in Crimea but did not provide additional details.

An anonymous source at HUR told the Ukrainian public broadcaster that the agency “systematically” attacks Russian digital infrastructure, including internet providers.

In May, Ukraine’s military hackers claimed responsibility for an attack on a major internet provider in the Russian city of Belgorod, located about 20 miles north of the Ukrainian border. The targeted company allegedly provides services to state and military institutions.

The attacks on Russian internet providers are also carried out by other Ukraine-linked hacker groups. Last October, a group of cyber activists known as the IT Army claimed responsibility for bringing down Miranda Media and two other Russian internet providers operating in Crimea.

At that time, Miranda Media stated that the attack was “carefully planned by cybercriminals.”