The company has likely offered the cargo through private negotiations and it was not immediately clear if it was a firm offer, one of the sources said.

NLNG, set up 16 years ago to export gas, is owned by Nigerian state oil firm NNPC, Shell, Total and Eni.

NLNG can produce 22 million tonnes of LNG a year and has long-term supply contracts with Italy's Enel, Shell, France's Engie and Portugal's Galp, among others. It also sells on the spot market.