Witnesses said a middle-aged man carried a gasoline can into the Longfei Inn, set it on fire and left quickly.
The small hotel, located in Harbin's Daoli district, is in the basement of a seven-floor residential building.
But it has no fire fighting equipment, according to residents living in the building.
The fire has been extinguished, and the injured rushed to hospital for treatment.
Local police are investigating the case, state-run Xinhua news agency reported.
