China is restricting the number of its citizens allowed to travel to Tibet as Beijing celebrates the 60th anniversary of the region's "peaceful liberation", travel agencies told AFP Saturday.
The agencies also confirmed that the troubled area had been closed to foreign tourists from June and the ban would last until the end of July.
"Half as many plane and train tickets have been sold" as the usual number, the Tibet General Travel Agency told AFP.
"It's hard to buy tickets" for Tibet, an employee from another agency, Qinghe Tibet, said. He added that "security was tightened on the roads leading to the 'Roof of the World', especially on the highway between Qinghai Province and Tibet" while checkpoints had multiplied inside the Tibet Autonomous Region.
"The sale of tickets has been limited," an official from China Travel Tibet added.
The three agencies confirmed information given last month by other tourist industry workers to AFP that Tibet was closed to foreign travellers during the celebrations of 60th anniversary of the entry of Chinese troops into the area.
Gao Yang, Beijing's top official in the region, said Friday in its capital Lhasa that Tibet had received 2.25 million Chinese and foreign tourists in the first half of the year, up nearly a quarter on the same period last year.
He added that "overall" the celebrations "would not affect the development of tourism in Tibet".
The International Campaign for Tibet (ICT) said Saturday that Lhasa was "virtually cut off from the rest of the world" because of the official ceremonies.
Religious activities have also been restricted, the ICT said, adding that the path used by the Buddhists around the Potala, the former residence of the Dalai Lama, was rendered inaccessible by the construction of a large stage.
Tensions run deep in Tibet, where many Tibetans accuse the government of trying to dilute their culture, citing concerns over what they view as increasing domination by China's majority Han ethnic group.
Disquiet spilled over into violent anti-government riots in Lhasa in March 2008, which then spread to neighbouring provinces with significant Tibetan populations.
In the wake of the 2008 unrest, foreign tourists were banned from travelling to the Himalayan region for more than 12 months.
In March this year, Tibet was once again closed to foreigners ahead of the third anniversary of the riots, but travel agencies said overseas visitors had been able to visit from April to June.
Even when foreigners are allowed in, authorities require them to obtain special permits - in addition to Chinese visas - and also travel in tour groups.
China, which says living standards in the region have improved markedly since it started ruling the region in 1951, has increased security in Tibetan areas since the 2008 unrest.
But reports of unrest still surface. One region in the southwestern province of Sichuan was hit by demonstrations earlier this year after a Tibetan monk self-immolated and died in an apparent anti-government protest.