Bahrain has received bids from only three firms to explore for oil in the kingdom's waters, the country's oil minister said on Thursday.

At least 18 companies had earlier expressed interest.

Bahrain has previously explored for oil in its waters but found very little. The kingdom hopes new advances in technology may yield better results.

US firm Occidental, Russian state-owned Zarubezhneft and Thailand's PTT Exploration and Production PCL submitted bids by Wednesday's deadline, and winners will be chosen by the end of the year, the Minister of Oil and Gas Affairs Abdul-Hussain bin Ali Mirza told Reuters.

"We are very pleased. This is only for the offshore...four exploration blocks. Any one of these bids could be for all four," Mirza said.

Bahrain has also invited bids to revamp its onshore operations, which are due by October 17.

In March, Mirza said 18 firms had expressed an interest in either one or both tenders, and in July media reports said about 25 firms had shown an interest for offshore exploration rights.

Mirza said no dollar figure had been attached to the bids, and that they were being evaluated on a technical basis.

He declined to say how much more oil Bahrain hoped to extract from the offshore blocks, or give bidding details for its onshore tender.

Bahrain produced about 35,000 barrels per day (bpd) from its Awali oilfield in 2006. It received another 150,000 bpd from Saudi Arabia, its share of output from the Abu Saafa oilfield. - Reuters