A boy jumps off a tree into the Rio Negro River in Sao Pedro, near Manaus, Brazil. (AP Photo/Felipe Dana)

Rio de Janeiro - The Amazonian city of Manaus, one of the 12 host cities of the upcoming World Cup in Brazil, declared a state of emergency Tuesday after the local Negro river burst its banks.

The water reached 29.19 metres and threatened to flood several neighbourhoods in the capital of the Brazilian state of Amazonas.

Manaus Mayor Arthur Virgilio Neto said the city needs federal funds to support families who are set to be preventively evacuated until the water level goes back down.

Virgilio Neto said the decision to declare a state of emergency was based on research carried out by the Civil Defence and by geologists, who predicted that water levels could rise by another 30 centimetres by July and may flood several of the city's neighbourhoods.

He insisted, however, that this would not affect the World Cup, since the city has built a 2,600-metre network of bridges for cars and pedestrians to ensure urban mobility during the tournament in the event of flooding.

The new Arena Amazonia stadium is set to host four group-round matches: England-Italy on June 14, Cameroon-Croatia on June 18, United States-Portugal on June 22, and Honduras-Switzerland on June 25.