The restart of German utility Uniper's troubled Berezovskaya 3 plant in Russia has been further delayed, the company said on Thursday, citing coronavirus-related quarantine measures.

The 800 megawatt lignite unit, which was damaged by a fire more than four years ago, is now expected to resume commercial operations at the end of the year, having previously been scheduled for a third-quarter restart.

Uniper, which is majority-owned by Finland's Fortum, said that work on the station, which is run by Uniper's Russian subsidiary Unipro, is being disrupted by strict quarantine measures.

The unit has been out of service since February 2016, taking roughly 120 million euros out of Uniper's annual operating profit, said finance chief Sascha Bibert.

"This has been painful for Uniper," Bibert told reporters. His predecessor Christopher Delbrueck in 2017 flagged a restart of the unit in the third quarter of 2019.

The update on the plant came as the company reported that first-quarter operating profit more than tripled to 651 million euros, boosted by its gas business and higher power prices.

(Reporting by Christoph Steitz, Vera Eckert and Tom Kaeckenhoff; Editing by Michelle Martin and David Goodman)