Azeri Light, one of the main lighter grades that competes with Libyan barrels, has been discussed around $2.10-$2.40 a barrel above dated Brent this week, the highest since November, though there were no bids or offers in the Platts window on Thursday.

Traders said Azerbaijan's main export grade may face some pressure from a preliminary February loading programme on Thursday showing Azeri Light exports rising to 821,000 barrels per day next month from 742,000 bpd in January.

Azeri has been boosted by lower supplies from Libya, with exports down to less than 300,000 barrels per day from closer to 900,000 bpd in October, with fears the country is slipping into all-out civil war between two main rival factions.

Overall markets remain well supplied, however. Some of the world's largest oil traders have this week hired supertankers to store crude at sea, marking a milestone in the build-up of the global glut.

Trading firms including Vitol, Trafigura and energy major Shell have all booked crude tankers for up to 12 months, freight brokers and shipping sources told Reuters.

No bids or offers were seen for Russia's main export grade Urals in the Baltic or Mediterranean, leaving prices around $2.40 below dated Brent and $1.90 below respectively. Swaps have this week indicated southern cargoes are expected to weaken to be closer in line with those in the north.

In Kazakhstan's CPC Blend, prices held about 70 cents a barrel below dated Brent. Vitol offered a cargo for loading Jan. 27-31 at dated Brent minus 40 cents, but then withdrew.