BEIJING — Chinese travel agents organizing trips to Tibet said Monday they have been ordered not to receive foreign visitors around the March 14 anniversary of a bloody anti-government riot in 2008.

Beijing Youth Travel Service saleswoman Li Jianyue said the order was conveyed verbally, as is often the case with official directives that the government does not wish to defend or explain.

"A few days ago, they told us not to organize the foreign groups this month," Li said.

Liu Qiang, a sales manager at Kangqu International Travel Agent in Tibet's capital, Lhasa, said his company was notified of the measure in January.

Hotel receptionists reached by phone in Lhasa on Monday also said foreigners were barred from the beginning of the month. The receptionists and the travel agents said the impact would be minimal since the Himalayan region's bitter winter tends to make March a low season for tourism.

However, a receptionist at the Jardin Secret Hotel in Lhasa said the ban could last for up to three months.

"This has grown into a yearly practice around March 14 every year," said the woman, who would give only her surname, Dong, to avoid drawing the ire of authorities.

Calls to the Tibet Tourism Bureau and Foreign Affairs Office in Lhasa rang unanswered Monday. A regional government spokesman, Fu Jun, took down a question about the ban and said he would look into it.

China strictly limits access by foreigners to Tibet, requiring them to obtain special permits in addition to their Chinese visas and to travel in tour groups.

Tourists from outside the country were banned entirely for more than a year following the 2008 riots in Lhasa that left at least 22 people dead and set off a wave of protests across Tibetan areas of western China.

China responded with a massive military crackdown in which Tibetan rights groups say nearly 140 Tibetans were killed.

China blamed followers of Tibet's exiled Buddhist leader the Dalai Lama for fomenting the disturbances, a charge the Buddhist leader denies.

China says Tibet has been part of its territory for at least centuries, while many Tibetans say they were effectively independent for most of that time.