TAGONG, China (Reuters) - Chinese police have discovered explosives under a bridge in Tibet, sources said on Tuesday, as ethnic Tibetan villages high in the grasslands of far western China faced tense New Year celebrations.
Almost a year after deadly riots erupted in Tibetan capital Lhasa and triggered unrest in neighboring provinces, Chinese security forces remain on high alert a day before the holiday, which varies from year to year and this year begins on Wednesday.

Police had recently found several kilograms of explosives under a bridge in Tibet's eastern Changdu, or Qamdo, prefecture, bordering Sichuan province, two sources with knowledge of the case said.

"Police are investigating," one of the sources told Reuters. "No arrests have been made," added the source, who declined to be named for fear of reprisals. No other details were available.

Calls placed to the Qamdo government and police could not be connected. The Tibetan propaganda office was also unavailable for comment.

The prefecture's Communist Party chief told officials at a work conference to be vigilant in the face of a "grim situation in the struggle against splittism," according to a notice seen on the local government's website (www.changdu.gov.cn) on Tuesday.

Senior police in the regional capital, Lhasa, had also met to "mobilize and fully deploy" for 2009, said a report on the region's official news website (www.chinatibetnews.com).

A Reuters reporter in Kangding in neighboring Sichuan province was told by an official from the local foreign affairs office he should not venture deeper into the heavily Tibetan region due to "landslides and cold weather."

In even more remote communities, communications have been cut and banners warn residents to banish all thoughts of separatism.

"You should understand that the atmosphere this year has been affected ... because a lot of Tibetans are in jail and also because of these incidents," said Sunom Cherong, a 31-year-old monk pausing to pray at a monastery in Tagong, a village nestled in a treeless valley a bone-jarring bus-ride from Kangding.

The heightened security comes ahead of another sensitive date -- the 50th anniversary of the exile of Tibet's spiritual leader, the Dalai Lama, who fled to India after an abortive uprising against Chinese rule in 1959.

RELAY DISRUPTED

China brands the Dalai Lama a separatist and accuses him of being behind anti-China protests that followed last year's violence and disrupted the international Olympic torch relay. The Dalai Lama denies the charges.

In nearby Yajiang, a small farming village perched on the vertigo-inducing road to Tibet, banners warn residents: "Say no to separatism, maintain stability and promote development."

The village's Internet cafe remains empty and residents complain of a lack of mobile phone services.

"I cannot get on to the Internet and also I cannot get much of a connection and service for my mobile phone here," said 19-year-old Liao Dawei.

Further along the road to Tibet in Lithang, Chinese forces detained up to 24 Tibetans for taking to the streets shouting support for the Dalai Lama, an overseas rights group said earlier this month. Local police denied any knowledge.

The protests were sparked by the arrest of a Tibetan who called for a boycott of New Year celebrations, the group said.

The boycott has received a mixed reception among local Tibetans, many of whom speak fluent Mandarin and pass national holidays with their ethnic Han majority neighbors.

In Tagong, Sunom Cherong said monks would mark the holiday as usual amid the security clampdown -- in quiet contemplation.

"There will be prayers ... In a historical sense, we have never stopped doing prayers. So I think these problems will not affect us," he said.