Tickets for the Rio Olympics have gone on sale with the first batch of a total 7.5 million tickets made available online to thousands of fans.

The sales process for Brazilian nationals and residents started on Tuesday after organisers last week released a detailed competition schedule for each sport allowing fans to seek out their favoured events.

Fans were asked to choose based on sport, game day and event site, give their financial details and apply online via the official web portal, www.rio2016.com portal.

One missing element was tickets for football matches due to be held in Sao Paulo amid a dispute with Corinthians football club, owners of the Corinthians Arena, over who must pay

for "overlay" costs to adapt the venue for the Olympic tournament.

The club wants local government to stump up funds running to an estimated $US10 million ($A13.09 million), though the figure is widely disputed.

The football event is the only sport to host action outside Rio owing to the amount of matches.

World governing body FIFA has given the green light to six cities and seven stadiums - Rio, Salvador, Brasilia, Belo Horizonte, Manaus in Amazonia and Sao Paulo.

Porto Alegre in the south and Fortaleza in the northeast are possible stand-in options should Sao Paulo ultimately be dropped - but organisers insist there is "no plan B."

A source on Tuesday said: "Sao Paulo football tickets will be included in due course once negotiations are completed."

Home fans had to register via the official website for the initial sales phase running to April 30.

Seventy per cent - or 5.2 million - tickets have been earmarked for Brazilian residents, millions of whom will be eligible for discounts and also able to pay in up to five monthly instalments.

Foreign fans must apply through a separate process for the August 5-21, 2016 extravaganza, South America's first ever Olympiad.

A real time, first come first served, sale of remaining tickets will follow from October for Brazilians and Brazil residents.