KYIV/LONDON (BLOOMBERG) - A power plant in eastern Ukraine is at risk of shutting down because of a fire that started during "constant shelling", according to DTEK Energy, a utility owned by Rinat Akhmetov, the nation's richest man.

The facility in the Luhansk region, which is close to the contact line between Ukrainian army and Russia-backed separatists, is the biggest local producer of electricity. It's been under attack during the past 24 hours, with critical staff being evacuated to the bomb shelter, the company said on Tuesday (Feb 22).

The town of Shchastya, where the power plant is located, was without electricity and heating as of 9.20pm (3.20am Wednesday Singapore time), the company said. At least 11,500 people have been affected, and nearby locations are also facing electricity cuts.

The blaze "cannot be localised" due to the shelling, and the state emergency services said fire engines has to turn back due to the shelling. It's unclear where the attack was coming from.

A cease-fire at the contact line with separatist regions in eastern Ukraine has always been shaky, with thousands of violations each year, according to international monitors. Russian President Vladimir Putin ratcheted up tensions this week by announcing he's recognising two of Ukraine's self-proclaimed republics including Luhansk.

On Monday, Ukraine reported damage to a natural-gas treatment plant in the region. The facility, which isn't connected to a major network transiting Russian gas to Europe, was shelled by mortars fired from separatist territory, and a village was cut off from its gas supply, state-run energy company Naftogaz Ukrainy said in a statement.