In pictures: Ice festival

The festival, in Harbin in the far northeast of China, has become the city's biggest individual source of income since it was launched in 1985.

But that income is under threat because the ice sculptures are starting to melt much earlier than usual.

Last year, Harbin's average temperature was 6.6C, the highest on record.

'Worried'

Harbin is one of China's coldest cities. In winter, temperatures can drop as low as -35C.

Despite its harsh climate, the city has used the snow and ice to its advantage, and turned itself into a popular winter tourist destination.

Visitors arrive from across Asia to experience the numbing cold and see the city's ice sculptures.

This year the festival has an Olympic theme, to celebrate Beijing hosting the Olympic Games.

Animals, people, even famous buildings are turned into intricate sculptures that are lit up at night.

But higher local temperatures mean that even in January the midday sun starts to melt many of the sculptures.

And the warmer weather is reducing the length of the tourist season.

Sun Lei, an official involved in the festival, told the BBC that the festival traditionally runs until the end of February.