Fire fighters Zhu Xiaolei and Zhang Yu died while searching for people who could have been left stranded in the fire, Xinhua quoted local fire officials as saying.
The 12-storey Dehui International Plaza normally houses thousands of people in its shopping centre and the upper office floors.
The fire reportedly began shortly after 8pm local time, as the shopping area was preparing to close.
After battling the blaze for several hours, by Thursday morning firefighters had been forced to retreat from the main fire fearing the tower may collapse.
Instead they focused their efforts on putting out the fire in a neighbouring hotel where it had spread from the Dehui building.
An office block fire in Ürümqi, northwest China has claimed the lives of three firefighters and injured a fourth. The 12-storey dual-purpose office and market building was completely destroyed in the blaze, which also spread to and severely damaged an adjacent hotel.

According to a spokesman for Xinjiang fire brigade, an eyewitness reported that the fire, which started at around 8:20 p.m. local time on Wednesday night, originated in a stall selling mops on the first floor of the Dehui International Plaza. According to a security guard, the building had been emptied of customers 20 minutes before and consequently few people remained in the building at the time of the fire. Fire crews arrived within 15 minutes of the fire starting.

The plaza's basement up to its fourth floor contained a total of approximately 2,000 stalls selling items such as clothes, cosmetics and toys. Floors five to 12 housed offices.

All 12 floors were engulfed by fire, and fire crews eventually abandoned efforts to tackle the conflagration amid fears of a collapse. The fire continued into Thursday afternoon, but has since been controlled. It burned for a total of nearly 22 hours. A neighbouring 20-storey hotel also caught fire; only the seventh floor was affected before the second building was put out. All guests were evacuated.

As of 6:30 p.m. there was still much smoke in the area, but no visible flames. Rescue workers remained unable to access the building due to continued intense heat. A total of 435 fire fighters and 84 fire engines were involved in the emergency response. 100 firefighters continue to check the hotel for any small fires, which may remain to be extinguished. Structural measures have been undertaken to prevent the steel framed plaza from collapsing when the metal comes into contact with cool night air, which typically falls to temperatures of minus 20 degrees centigrade.

The injured fireman has been hospitalised and is in a stable condition. The deceased were identified as Zhu Xiaolei, Zhang Yu and Gao Feng. They had been conducting a search of the building to check for anyone who may have been trapped. Feng was initially considered missing, but was subsequently confirmed to have died. It is presently believed no civilians were injured in the blaze.

A quantification for the value of damages caused is not yet available. Authorities have launched an investigation into the disaster.