With sirens blaring, more than 20 fire engines broke up the weekend mood in Tokyo's busy Shibuya district Saturday evening as firefighters arrived to extinguish a blaze at a building near the station.

No one was injured in the fire, which broke out around 6:20 p.m. at a barbecue restaurant on the fourth floor of an eight-level building just 80 meters away from the JR Shibuya Station's west exit.

Restaurant staff and customers were forced to evacuate from a nearby building in an area where restaurants and bars are clustered together.

The fire charred an air duct, as well as about 10 square meters of the top floor.

"At first, I saw a large amount of black smoke rise" from the building, said one male witness from Tokyo's Setagaya Ward. "The I heard a loud 'bang, bang, bang,' which was really startling."

Another witness, a clerk at a musical instrument shop near the site, said: "I heard an explosion and a crash, and then people nearby started to run away from the building."

The Tokyo Fire Department and Shibuya Police Station have yet to determine the cause of the blaze.