At least seven people have been killed in an accident at one of South America's biggest tourist attractions on the border between Brazil and Argentina.

The tragedy occurred when two boats full of tourists collided during an excursion underneath the Iguacu Falls.

The 80m-high falls are a magnificent spectacle, with 275 water falls plunging into the foaming Iguacu River.

Tourists to South America usually describe it as one of the highlights of their trip, made all the more exciting by the ride in the inflatable launch, which takes visitors right underneath the falls.

Under normal circumstances, the only real risk is of getting soaked to the skin, but on this occasion, something went badly wrong.

Excursions cancelled

It seems that two boats - one of them carrying more than 20 people - collided during an excursion.

One report says that the larger vessel rode straight over the smaller one, killing the pilot and six foreign tourists.

The dead foreigners are reported to come from France, Portugal and Chile.

The tour operator responsible has not made any comment for the time being, but the Brazilian environmental agency, Ibama, which looks after its side of the Iguacu National Park, says that no more such excursions will take place until the circumstances of the accident are cleared up.

Investigations are being carried out by the Brazilian federal police and the navy.