TOKYO (AFP) - Two people, including a 10-year-old boy, died on Monday from injuries sustained in an explosion at a fireworks festival in Japan last week, bringing the death toll to three, police said.

The victims were among some 60 people injured in the blast which ripped through food and drink stalls set up to entertain visitors at the annual festival outside the ancient capital of Kyoto on Thursday, police said.

Sora Yamana, 10, died early on Monday while a 35-year-old man, Naoki Kuroda, passed away shortly after noon in hospital, a local police spokesman said.

A 44-year-old woman who suffered severe burns died on Saturday.

Police earlier said 18 people were seriously injured from burns.

The top-selling Yomiuri Shimbun daily said on Monday that a 13-year-old boy and eight-year-old girl were still in serious condition in hospital.

Police suspect that the explosion occurred when a vendor at one of some 350 stalls at the site opened the cap of a petrol container to refill an electric generator, press reports stated.

The highly pressurised petrol was sprayed over a wide area, causing gas cylinders to explode as three of the stalls went up in flames.

The vendor was expected to be investigated on charges of professional negligence when he recovers from severe burns he also suffered in the accident.