(Adds detail to Nov. 26 story on contract expiry, shares)

FRANKFURT/DUESSELDORF, Nov 27 (Reuters) - Uniper has to pay 550 million euros ($600 million) to a European supplier of liquefied natural gas, the German state-owned utility said on Sunday, citing a ruling by an arbitration court over a contract concluded before the group's spin-off in 2016.

The arbitration proceedings, under the rules of the International Chamber of Commerce, began in early 2021 and relate to the pricing provisions of a long-term LNG supply agreement with an undisclosed counterparty, Uniper said.

Spun off from E.ON in 2016, Uniper last year launched legal proceedings against Russia's Gazprom, its former main supplier of natural gas, which first cut and later suspended deliveries, causing Uniper to nearly collapse.

The LNG contract in question expired in 2022, Uniper, one of Europe's biggest gas and LNG traders, said, adding that therefore no further financial fallout was to be expected.

Thinly-traded shares in the group, which became Europe's most high-profile corporate victim during last year's energy crisis, were up 1.4% at 1058 GMT.

Uniper said the fine "related to the retroactive re-pricing of the long-term agreement", without being more specific. Arbitration proceedings over gas supply contracts are not uncommon in the industry.

Uniper, which was bailed out by Germany last year, said the payment would impact its annual results, adding it was currently analysing the decision and would review legal steps. It did not provide an updated fiscal outlook.

Uniper in October confirmed that it expects adjusted earnings before interest and tax of 6 billion to 7 billion euros and adjusted net profit of 4 billion to 5 billion euros in 2023 thanks to lower-than-expected gas spot prices.

($1 = 0.9168 euros)

(Reporting by Christoph Steitz and Tom Kaeckenhoff Additional reporting by Gokul Pisharody in Bengaluru; Editing by Josie Kao, Lisa Shumaker and David Evans)