Four of the people killed in Siem Reap were children who had been sleeping in apartments on an upper floor of the building, located on the site of the popular night market.
Police Chief Sath Nady told Britain's Sky News the eight victims had been trapped in the building when the fire broke out.
The fire, which was blamed on an electrical problem, destroyed more than 100 stalls and forced the popular market to close.
Siem Reap, in northwestern Cambodia, is considered the gateway to the ancient temple complex of Angkor, a major international tourist destination, Sky News said.
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