A Chinese shipbuilding firm will construct 18 ultra-large liquefied natural gas (LNG) transport ships each with a payload capacity of 271,000 cubic meters for Qatar.

The deal for the world's largest single shipbuilding order between China State Shipbuilding Corporation (CSSC) and QatarEnergy was signed Monday.

The LNG transport ships are dubbed "sea-going super refrigerated trucks" that carry LNG at temperatures as low as minus 163 degrees Celsius. Such ships are among the most challenging ship types to construct in the world.

The 271,000-cubic-meter LNG transport ship has a total length of 344 meters, a breadth of 53.6 meters, and a depth of 27.2 meters, making it the world's largest LNG transport ship. Compared to conventional 174,000-cubic-meter LNG transport ships, it boasts a 57 percent increase in carrying capacity.

The ships will be independently designed and constructed by Hudong-Zhonghua Shipbuilding, a subsidiary of the CSSC.