Police said one person had been left in a serious condition by the blast, which happened in Sapporo, the capital city of Japan’s northern main island Hokkaido.
A number of people have also been reported as missing, while others have been rushed to a nearby hospital, BNO News said.
It is not yet known what caused the explosion, which appeared to come from a restaurant in the area just before 8.30pm local time, on December 16. Images on social media initially showed flames rising from the area with debris scattered across the ground.
Emergency services then arrived and firefighters could be seen tackling collapsed buildings. Police have now sealed off the area amid fears of another blast.
Japanese broadcaster NHK said the area affected had both residential and dining establishments and was about 3km south-east of the city centre.
While The Japan Times quoted one eyewitness in his 50s, who said:
‘I heard a bang which sounded like thunder and my condo was shaken.’ Another eyewitness told NHK that the blast had broken the windows of the restaurant he was working in, and that there were ‘many injured people’