A least 20 people died and two were injured when fire engulfed a third-floor karaoke bar in one of Indonesia's largest cities on Friday, police said, adding that the death toll could rise.

Fire fighters contained the blaze in the multistory building in Medan on Sumatra island and extinguished it within hours, fire brigade spokesman Mohammad Zein said.

The bar had been filled with hundreds of patrons, local media reported. More victims could still be found in the debris, police chief Maj. Gen. Badrudin Haiti said.

The two wounded were in critical condition at local hospitals, Haiti said.

He said human error could not be ruled out as the cause of the fire.

Some witnesses told local television that the blaze was caused by an electrical short circuit.