UPDATE 1-Norway's Troll gas output down due to safety issues

* Output from Troll field reduced by 30 mcm/d

* Kollsnes gas processing plant

(Adds Statoil, power outage, analyst, gas flows)

OSLO, Oct 12 (Reuters) - Output from Statoil's Troll natural gas field offshore Norway has been reduced due to safety issues, gas system operator Gassco said on Friday, raising concern about supply safety after a string of outages.

The shutdown comes after a series of supply disruptions at Norway's key gas processing plants over the last two weeks, which pushed UK gas prices higher and left traders worried about stability of deliveries in the upcoming winter.

The 145 mcm capacity Kollsnes gas plant that processes gas from Troll for export to Britain and Europe reported power consumption dropped to 50 MW from 270 MW, indicating a sharp reduction in production.

A Statoil spokesman declined to comment.

A spokeswoman for Norway's Petroleum Safety Authority said the watchdog not notified about any safety issues.

Companies have to inform the safety authority only about major incidents, she added.

Still, the outage is going to boost market anxiety.

"The volatility of Norwegian gas flows to the UK during recent weeks is a source of concern," Dragos Talvescu, an Oslo-based analyst at consultancy Sund Energy, said.

"If that happens during winter time, there could be panic and large spikes in the UK prices," he added.

The Gassco-operated Kollsnes plant also processes gas from the Kvitebjoern, Visund and Fram fields.

Gas flows from Norway at 1100 GMT were not affected, data from Gassco showed. The Langeled pipeline, UK's main subsea gas import route fed by the Nyhamna processing plant, was pumping 70.8 mcm of gas per day.

Outages in production are not immediately reflected in the flows because there are large gas volumes in the pipelines.

(Reporting by Nerijus Adomaitis; editing by Balazs Koranyi and Keiron Henderson)

((nerijus.adomaitis@thomsonreuters.com)(+47 9027 6699)(Reuters Messaging: nerijus.adomaitis.thomsonreuters@reuters.net))