President Xi Jinping on Monday sent a message to his Russian counterpart Vladimir Putin to express condolences over a massive shopping mall fire that killed at least 56 people in Russia's south central city of Kemerovo.

In the message, Xi said he was shocked at the news of the fire, which caused huge casualties and property losses.

On behalf of the Chinese government and the Chinese people, and also in his own name, Xi deeply mourned those killed in the fire and showed sympathy to the bereaved families and those injured.

Premier Li Keqiang also sent a message to his Russian counterpart Dmitry Medvedev to express condolences over the fire.

At least 56 people were confirmed dead in a major fire that broke out in a shopping mall in the south central Russian city of Kemerovo on Sunday, the Russian Investigative Committee said Monday.

The fire, which started Sunday afternoon, has been put out, but rescuers are still struggling to reach the upper floors because the roof of the four-story building collapsed.

A total of 44 people requested medical treatment and 10 of them remain in hospital in the Siberian city, the committee said in a statement.

An 11-year-old boy who jumped out of the window from the 4th floor suffered severe injuries, according to Health Minister Veronika Skvortsova.

The exact number of the missing is unknown. Previous reports said 64 people were missing, including 41 children.

Earlier TV images showed black smoke billowing from the Winter Cherry shopping center, a business complex that also houses a cinema which is usually packed with audience on Sunday afternoons.

A total of 663 people took part in the search and rescue operation, the Emergencies Ministry said, adding that work is complicated by strong gas contamination, high temperatures and dense smoke.

The Investigative Committee said that four people were detained and interrogated, including the tenants of the premises where fire possibly started and the head of the management company servicing the building.

Russian President Vladimir Putin extended condolences to the families and friends of the victims on Sunday and ordered related authorities to provide all necessary help.