China has introduced a heavy police presence into Tibetan regions of the country ahead of the start of Tibetan new year celebrations on Wednesday, the first in a number of potential flashpoints over the next month.

The 15-day festival, called Losar, is usually one of most festive times of the year for Tibetans, but this year there has been an underground campaign to boycott the celebrations to mourn those killed during the wave of protests in the region last year.