UPDATE 1-Japan's Idemitsu to buy UK oil explorer Petro Summit

* Buys oil explorer from Japan trading house Sumitomo

* Move expands Idemitsu's stakes in North Sea oil fields (Adds details)

TOKYO, Nov 13 (Reuters) - Idemitsu Kosan Co (5019.T), Japan's third-largest refiner, said on Friday it would buy British oil explorer Petro Summit Investment UK Ltd, a subsidiary of Japanese trader Sumitomo Corp (8053.T).

Petro Summit produces approximately 5,000 barrels of oil equivalent per day (boed) on a rights ownership basis in the British North Sea.

The deal adds to the 28,000 boed Idemitsu already produces in the Norwegian North Sea.

An Idemitsu company official declined to comment on the purchase price of the deal, but it is estimated to be several tens of billions of yen. (Reporting by Osamu Tsukimori)