XINING - China will increase passenger train services from major cities to Lhasa to cope with a travel surge that has rippled across the Qinghai-Tibetan Plateau since a landmark railway opened six years ago, railway officials said Sunday.

Trains will travel daily between Guangzhou, capital of South China's Guangdong province, and Lhasa starting from July 9, said Wang Tao, a spokesman for the Qinghai-Tibet Railway Company. Chengdu-Lhasa trains will soon follow the same schedule.

Seven major Chinese cities currently have Lhasa-bound trains. All are expected to operate on a daily basis in the future, Wang said. Among them, Beijing, Shanghai and Xining already have daily trains to Lhasa.

The Qinghai-Tibet Railway, spanning 1,956 km from Xining to Lhasa, has transported 52.76 million passengers since going into operation on July 1, 2006, said Bao Chuxiong, general manager of the Qinghai-Tibet Railway Company.

Bao said railway has become the "first choice" for most Tibet travelers.

The number of Qinghai-Tibet Railway travelers has grown by about 10 percent annually, he said. Last year, it reached 10.6 million, up 65.6 percent compared to the figures from 2006.

But the increase has strained railway operators, as there are not enough oxygenated trains to meet demand, said Ma Xiaojun, another official with the Qinghai-Tibet Railway Company.

Because of the low oxygen content on the Qinghai-Tibetan Plateau, trains traveling on the railway have to use sealed and oxygenated train cars. Currently, all Lhasa-bound passengers board oxygenated trains from the departure city, but this arrangement will become impossible when all services are offered on a daily basis, Ma said.

Starting this month, passengers on Guangzhou-Lhasa trains will need to switch from ordinary trains to oxygenated trains at the Xining railway station, just as they would transfer between flights in an airport, he said.

"The mass transfer, usually involving hundreds or even thousands of passengers, is really a scene to watch," the official said. "The railway station operators have undergone many drills to be prepared."

Railway officials said that if the transfers work properly, efforts to increase Lhasa-bound train services will be expedited so that people can easily ride a train to Tibet from any Chinese city connected to the country's railway network.

Ji Kangping, a researcher with the Academy of Social Sciences in Qinghai, said the railway has become an important driver for the region's economy. The number of domestic tourists to Tibet has grown particularly fast in recent years, he said.

According to the Tibet Tourism Bureau, the region received 8.6 million tourists last year, about seven times the number received before the Qinghai-Tibet Railway opened. Tibet aims to attract 10 million tourists this year, with tourism revenues expected to reach 12 billion yuan ($1.89 billion), the local government said.