More than 6.5 million people traveled on the world's highest railway, the Qinghai-Tibet railway, in 2011, up 9 percent from 2010, the railway company said Tuesday.

The high-elevation railway that connects Xining, capital of Qinghai Province, to Tibet's capital of Lhasa, also transported 40 million tonnes of cargo in 2011, up 8 percent year-on-year, said an official with the Xining-based Qinghai-Tibet Railway Company.

The official said the number of passengers is likely to reach 6.9 million this year.

Tibet Autonomous Region in southwestern China has seen tourism boom since the 1,956-km railway began operations in July 2006.

A total of 8.43 million tourists visited Tibet in the first 11 months of 2011, a 27.7-percent increase from the same period the previous year, according to Tibet's tourism bureau.