China has completed laying 421 kilometres of railway tracks for the 1,532-km long Qinghai-Tibet railway, the world's highest, the state media reported on Thursday.

Twenty-two of the 32 key projects have been completed or near completion. Work on laying 509-km main tracks, which accounts for 44.6 per cent of the whole length of the line, is already complete.

On August 9, track-laying of the Qinghai-Tibet Railway successfully reached the Tongtianhe Station.

The world's highest railway station will be located in a village two km west of Nagqu town in Tibet at an elevation of 4,500 meters.

Construction of the Nagqu section is considered the most difficult part of the whole project as the region lacks oxygen.

Qinghai-Tibet railway, reaching 5,072 meters above sea level at the precipitous Tanggula Range, links Xining, capital of northwest Chinese province of Qinghai, with Lhasa, capital of Tibet.

Till the end of July, yuan16.28 billion has been invested in the project.

The entire railway line is scheduled for completion in 2006.

Additional inputs from PTI