Torrential rains unleashed floods and landslides in the state of Rio de Janeiro Wednesday, leaving one person missing and playing havoc with commutes and air travel in Brazil's most iconic seaside city.

Sirens sounded in Rio's hillside slums as authorities declared a state of emergency and made preparations to evacuate areas threatened by landslides.

Residents of 43 favelas were urged to leave their precariously built homes as a precaution.

"A man has been reported missing in Nova Igua�u after he fell into a river at Realengo,", fire brigade colonel Sergio Simoes told broadcaster TV Globo news.

He said 18.8 cm (seven inches) of rain fell in the northern part of the state where Realengo is located.

One person was hospitalized after being pulled free from a landslide there and firefighters were working to pry loose another.

Simoes said there were reports of landslides at Anchieta, another town in the northern part of the state where two more people were reported trapped in rubble.

The rain also caused chaos in Rio, flooding some metro stations and bringing traffic to a standstill in the thoroughfare opposite the Maracana football stadium, which will host the World Cup final next July.

The foul weather force arriving flights to be diverted from the city's Santos Dumont airport.

Thousands of residents faced a struggle to get to work and Rio mayor Eduardo Paes advised people in the worst-hit areas to stay at home.

"The situation is critical -- we have had very heavy rain. Our priority is the alert system in the favelas (slums) and areas at risk of landslides," Paes told Globo News.

Over the weekend, torrential rain in the northeastern Brazilian state of Bahia left at least 16 people dead, a civil protection source told AFP. One person remains missing there.