An explosion and fire ripped through a four-storey building housing restaurants and bars in central Tokyo's busy Shinjuku entertainment district early today, killing 44 people, 32 men and 12 women, police said.
The area was packed with thousands of people beginning their weekends in one of Tokyo's most popular entertainment areas.
Police said the explosion ripped a hole measuring 1.5 metres by 0.5 metres in the wall of a They said the blast came from a parlour offering mahjong games, a popular pastime in Asia.
Witnesses said that stunned patrons raced out of the building and some were rescued from the roof by firefighters on ladder trucks.
Japanese media quoted police as saying that three men had fallen from the building, located near the well-known Shinjuku Koma Gekijo theatre.
"I saw a man jump off the building and thought it was a suicide. Then I saw smoke pouring out of the building," a man in his 20s told the television network, NHK.
Authorities said the injured had been rushed to nearby hospitals.
Forty seven people were rescued and taken to hospital, 35 of them in a critical condition and seven others were reported trapped inside the building in Kabukicho in Tokyo's Shinjuku area after the blast, news reports said.
The explosion happened after an employee at the mahjong parlour opened a door, police said, according to Kyodo News agency.
A number of survivors were rescued from the roof of the building by firemen with ladders.
Fire trucks and ambulances filled the narrow streets around the building, littered with broken glass and other debris from the building.
The number of casualties was the highest in Japan since 1982, when 33 people were killed and 29 others injured in a fire that gutted a hotel in the Akasaka area of central Tokyo. Police earlier said the death toll was 27, but a fire brigade spokesman said the latest toll had been confirmed at 44.
The fire brigade and police said that the cause of the disaster was not known and was being investigated.
NHK television quoted a witness as saying the blast sounded like it might have been gas-related.
Kyodo News agency said that building included a number of entertainment shops, including restaurants and sex establishments.
Kabukicho is one of Tokyo's busiest nightclub areas and is not far from the city's most crowded train station.
Crowds of onlookers gathered near the site to watch the rescue and firefighting operation. After putting out the blaze, firefighters concluded that there were no people left in the building, NHK said.
The reports said that the fire was on the third and fourth floors.