China's annual ice festival in Harbin has kicked off with couples lining up for a snow-themed mass wedding, swimmers braving frigid waters and frozen palaces rising from the ground.

Fireworks marked the festival's opening on Sunday night as tourists wandered between colourfully illuminated ice towers and monuments in the northeastern city.

Earlier in the day, 43 brides in lace wedding gowns and down jackets waited in line with grooms to take part in a "mass ice and snow wedding".

A few brave swimmers plunged into a pool carved from the frozen Songhua River on a day when temperatures stayed below minus seven degrees Celsius (19 Fahrenheit) even in the afternoon.

This year's Harbin International Ice and Snow Festival in the province of Heilongjiang required 170,000 cubic metres (six million cubic feet) of ice harvested from the Songhua River by more than 100 workers.

The workers toiled for hours on the ice each day in the weeks before the festival, cutting out thousands of pieces of ice every 12-hour shift.

The Harbin festival, featuring glittering palaces and fantastical scenes sculpted out of ice, has drawn millions of people over the years to one of China's coldest cities.

This year's festivities will coincide with the city's first skiing marathon this week, according to the official Xinhua news agency.

China has ramped up its promotion of snow and ice tourism ahead of the 2022 Winter Olympics in Beijing.

An expressway is under construction linking Beijing and Zhangjiakou, a city in northern Hebei province that will co-host the Olympics, while a high-speed railway line connecting the two cities opened on December 30.

China expects 340 million people to visit snow and ice attractions in the 2021-2022 winter season, up from 224 million in the 2018-2019 season, Xinhua reported Monday.

- This story accompanies a photo essay by Noel Celis -

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© Agence France-Presse