ISLAMABAD- Global trader Vitol on Monday placed the best offers for four of six cargoes of liquefied natural gas (LNG) sought by Pakistan in December, a source at Pakistan's procurement body said.

Vitol offered 16.9720%, 16.5513%, 15.9759% and 15.8761% of the price of Brent crude - known as a slope rate - for four deliveries in December, said the source at Pakistan LNG Limited.

The lowest offers for the two other cargoes were won by Trafigura TRAFGF.UL and Socar which offered Brent crude slope rates of 16.9870% and 16.8403% respectively.

Slope rates provide a price indication for the opaque spot LNG market.

The delivery windows for Vitol's shipments are Dec. 13-14, Dec. 18-19, Dec. 24-25 and Dec. 30-31. The windows for Socar and Trafigura are Dec. 3-4 and Dec. 8-9.

Last month Pakistan invited bids for a record six cargoes of LNG from the spot market for December, with authorities predicting a surge in the gap between demand and supply of gas in the winter. 

The South Asian country has a 15-year LNG purchase deal with Qatar to buy 3.75 million tonnes of LNG per year for 15 years to 2030, but it regularly taps the spot market.

It also has a five-year import deal with commodity trader Gunvor GGL.UL and a 15-year agreement with Eni.

(Reporting by Gibran Peshimam Editing by Edmund Blair and David Goodman) ((GibranNaiyyar.Peshimam@thomsonreuters.com; +923018217003;))