Ukraine is under siege by a major cyberattack which has crippled the government’s IT network. The cyberattack has affected airports, the Ukrainian central bank, the state power distributor Ukrenergo, the aircraft manufacturer Antonov, and two postal services.

The central bank said an “unknown virus” had hit lenders, but did not name those affected.

“As a result of these cyberattacks these banks are having difficulties with client services and carrying out banking operations,” the central bank said in a statement.

“The central bank is confident that the banking infrastructure’s defense against cyber fraud is properly set up and attempted cyberattacks on banks’ IT systems will be neutralized,” it said.

Rozenko Pavlo, the deputy Prime Minister, said he and other members of the Ukrainian government were unable to access their computers.

“We also have a network ‘down’,” he wrote. “This image is being displayed by all computers of the government.”

There are reports that the problem is not contained within Ukraine. Danish shipping company Maersk, Russia’s state oil giant Rosneft and Russia’s steelmaker Evraz also report disruptions from the “powerful” hack.

“We can confirm that Maersk IT systems are down across multiple sites and business units due to a cyber-attack,” the company said in a statement on its Twitter handle. “We continue to assess the situation. The safety of our employees, our operations and customers’ business is our top priority.”

This renewed spate of cyberattacks follow hacking attempts on Ukrainian state websites in late 2016, and repeated attacks on the country’s power grid, including one that left part of western Ukraine temporarily without electricity in December 2015. This has prompted security chiefs to call for improved cyber defenses.