UPDATE 3-Frontline says roughly 80 mln bbls oil stored at sea

(Adds oil trader comment)

By Stefano Ambrogi

LONDON Jan 16 (Reuters) - Norway's Frontline (FRO.OL), one of the world's biggest oil tanker owners, said on Friday oil firms were storing "about" 80 million barrels of crude oil at sea, possibly the highest in a quarter of a century.

The figure is the highest storage estimate reported to date. Ship broking houses, banks that trade oil and other industry sources believe the total is considerably lower.

"We think it's about 80 million barrels...but we are not 100 percent certain," the acting chief executive officer Martin Jensen told Reuters by telephone from Singapore.

Crude freight rates have been supported on top export routes by the slew of storage bookings. Tanker firms' profits are tied to the underlying cost of oil freight.

Mike Wittner of Societe Generale said the Frontline figure fitted the broader oil market picture.

"It's a big number, but its entirely plausible -- I don't see any reason not to believe him," Wittner said, adding the upshot was storage is significant and could easily grow even more.

Jensen said some 30 to 35 Very Large Crude Carriers (Very Large Crude Carriers) capable of carrying two million barrels each and 10 Suezmaxes with a capacity of a million barrels each were being used by oil firms for floating storage in the last few months.

The figures include oil tankers owned by oil majors which were being used to stockpile oil.

Jensen said most of the supertankers being used for "floating storage" were anchored in the U.S. Gulf, with others laid up in Asia and the Middle East Gulf.

"The Iranians have some and others are around Fujairah," he said.

Oil majors and independent trading firms have booked tankers in the last three months for storage to take advantage of a steep contango in the oil market [ID:nLC675700].

Major ship broking houses and industry sources contacted by Reuters since oil majors and traders began storing oil late last year give more conservative estimates for storage.

Most say oil firms are storing some 60 to 70 million barrels in total, more than 3O VLCCs worth of oil equivalent.

Oil industry sources say banks and hedge funds have been looking into taking tankers for storage, and some have made serious requests for ships.

But so far there is no hard evidence that they have booked tanker space.

"The truth is no one really knows exactly how much is being stored," one said. "We have a total of 14 VLCCs chartered in from the spot market. What the oil majors are doing with their own fleets we just don't know," he said. (Reporting by Stefano Ambrogi; editing by James Jukwey)