Tuesday's Troll A closure landed another blow to Britain's gas supplies that, combined with a shutdown at the country's North Sea Forties pipeline and a deadly accident at Austria's Baumgarten gas hub, caused prices to spike to four-year highs.

"We are preparing and checking our systems. We are on the activity of starting up the platform. It will be a gradual restart," Statoil spokesman Morten Eek said.

He declined to say if Troll A would restart production on Wednesday however, or when output would be fully restored.

Gassco, Norway's pipeline network operator that runs the Kollsnes gas processing plant, meanwhile said it expects gas flows from Troll to its facility to restart on Wednesday.

"We expect Kollsnes to start receiving gas today," a spokeswoman added.

The Troll field accounts for 40 percent of Norway's gas resources and is a crucial energy source for many European states.

(Editing by Terje Solsvik)

By Lefteris Karagiannopoulos