Three children and an elderly man drowned Saturday after playing in two different rivers in Japan as summer-like heat returned to many parts of the country.

A 7-year-old boy and his grandfather were pronounced dead after they were pulled out of a river in Takatsuki, Osaka Prefecture, police said.

The boy's two sisters, aged 9 and 11, were also rushed to the hospital after rescuers received an emergency call around 2 p.m. They were later reported to be in serious condition.

The boy, Taiki Kishishita, and his 73-year-old grandfather, Kunikiyo Shirotsu, were recovered from the river more than an hour after the emergency call, they said.

Meanwhile, two girls believed to be around aged 5 and 10 who were playing in a river in Toyota, Aichi Prefecture, died, local police said.

The police said two adults who were in the river with them nearly drowned but are not in life-threatening conditions.