OSLO, June 23 (Reuters) - Equinor's Hammerfest LNG plant in Arctic northern Norway has suffered an unexpected outage due to a sudden loss of power, halting all output, the company said on Sunday.

Production at Europe's largest liquefied natural gas export facility was halted late on Saturday and is expected to remain offline until 1900 GMT on Monday, according to a regulatory disclosure.

The plant's own power generators had been undergoing maintenance when its backup supply from an external grid failed, resulting in the outage, a company spokesperson said.

"We plan to restart on Monday," the spokesperson added.

Hammerfest LNG, also known as Melkoeya, has the capacity to deliver about 6.5 billion cubic metres of gas per year, enough to supply about 6.5 million European homes, and accounts for roughly 5% of all Norwegian gas exports.

Norway is Europe's largest supplier of natural gas after a sharp reduction in Russian deliveries since the start of the war in Ukraine in 2022.

The Melkoeya plant receives its gas via a pipeline from the Snoehvit offshore gas field. Its owners are Equinor, Petoro, TotalEnergies, Vaar Energi and Wintershall Dea. (Reporting by Nora Buli and Terje Solsvik; Editing by Bill Berkrot)