Asakura: Rescuers in Japan were scrambling on Friday to find more than 22 people missing after huge floods swept across the country's south this week, killing at least seven and leaving a trail of destruction.

Raging rivers overflowing with water and mud have devastated swathes of Kyushu - the southernmost of Japan's four main islands - after heavy rainfall, sweeping away roads and houses and destroying schools. The government on Friday said that seven had been killed, while 22 remain unaccounted for.

Public broadcaster NHK, however, reported that four additional bodies had been found in addition to the seven. NHK footage showed heavy machinery moving rocks and dirt to clean roads. A number of fallen trees were shown smashed into houses in the hard-hit Fukuoka prefecture city of Asakura, which saw more than 50 centimetres (almost 20 inches) of rain in a 12- hour period to Wednesday night. Vehicles could also be seen overturned or buried in mud and reinforced river banks destroyed by raging water. Military trucks and rescue vehicles competed for space on the city's streets.

Local authorities have dispatched helicopters to pluck people out of isolation, showing footage of stranded elderly residents being rescued. It added that local authorities were rushing to restore access to regions cut off by the landslides and floods. The government's top spokesman, Chief Cabinet Secretary Yoshihide Suga, told a press conference that some 12,000 police, military, firefighters and coast guard personnel were taking part in rescue operations. By Thursday they had recovered 522 people, and a further 15 on Friday.

Separately, Japan's Imperial Household Agency said that out of consideration for the disaster-hit region Emperor Akihito's eldest granddaughter Princess Mako and her fiancee decided to postpone the scheduled formal announcement on Saturday of their engagement.