An explosion ripped through a Moscow apartment tower Friday, blowing out exterior walls, sparking a fire and killing at least three people, officials said.

There was no immediate official word on the cause of the blast, but Russian media quoted unidentified officials as saying a gas canister might have exploded.

Smoke poured from apartments around the 10th floor of the 22-story building in northern Moscow. NTV television showed footage of at least three badly damaged apartments on three successive stories around the 10th floor, their blacked interior walls visible because exterior panels were blown out.

"I was parking my car and heard an explosion, turned around and saw fragments falling and a fire," a young man on the street said on NTV. "There was a smell of sulfur."

Footage showed flames leaping from at least two of the apartments and smoke billowing into the sky.

Yevgeny Bobylyov, spokesman for the Moscow branch of the Emergency Situations Ministry, later said the fire was extinguished.

The RIA-Novosti news agency, citing Moscow Mayor Yuri Luzhkov, reported that three people had been killed.

Television and news agency reports said residents were evacuated after the explosion.

Channel One television said a gas canister might have exploded.

Explosions and fires caused by accidents with gas stoves, heaters and gas canisters are common in Russia.

A spate of apartment-building bombings in Moscow and other cities in 1999 killed hundreds of people and were blamed on militant separatists. Chechen rebels have also been blamed or claimed responsibility for several bombings in the Russian capital in the ensuing years.