At least 500,000 foreign visitors arrived in Brazil to attend the Olympics in Rio de Janeiro, the government said on Friday, citing recent immigration figures that met a forecast made well before the games.

According to data compiled by federal police at immigration points and released to Reuters by the tourism ministry, a total of 572,961 foreigners entered Brazil between July 1 and August 15.

Although the Olympics began on August 5, the data goes back further to account for the arrival of many of the athletes, staff and other foreigners ahead of the games and related events.

Based on a separate survey compiled on behalf of the tourism ministry, which showed that about 84 per cent of those arriving in recent weeks were coming primarily for the Olympics, Brazil's government says it believes the forecast for half a million was met and possibly surpassed.

"The forecasts were right and could possibly end up being short of the total number," a tourism ministry spokesman said.

Despite many empty seats in Olympic venues throughout the games, which end on Sunday, foreign visitors have been out en masse across Rio de Janeiro - at competitions, on beaches, in restaurants, and at tourist sites.

Some Brazilians sought to blame the empty seats on foreigners rattled by bad publicity ahead of the event, from the scare over the Zika virus to concerns over crime and violence.

But the immigration figures suggest that demand from foreigners was robust.

Of about 6.1 million tickets available for the games, organisers say 70 per cent were reserved for locals. About 87 per cent of all tickets available were sold, but about a tenth of those purchased have been no-shows.

Some seats have remained empty because a plan by local officials to distribute free tickets to schoolchildren and charities did not in itself guarantee their attendance, especially in a city where transportation is costly and inefficient for many working-class residents.

"It's not really clear why there are no-shows, but from a sales perspective the demand has been alright," said Phil Wilkinson, a spokesman for Rio 2016, as the organising committee is known.

The recent immigration figures represent a 38 per cent increase over foreign entries in Brazil for the same period a year ago.

The tourism ministry official says a direct comparison of the two figures is misleading, however, because the jump in arrivals is offset, as it was when Brazil hosted the 2014 World Cup, by would-be visitors who steer clear - including many business travellers and more leisurely-minded tourists who are put off by big events. - Reuters