Brazilian citizens can buy tickets via the official Rio 2016 website while residents of other countries and regions must go through official ticket resellers in their respective countries and regions, reports Xinhua.
Tickets for 28 tennis sessions and handball finals were due to go on sale at midday local time on Wednesday.
Last week Rio 2016 organisers said 67% of the 7.4 million Olympic tickets on offer were already sold.
The first batch of tickets for the Rio Olympics went on sale in March last year. Prices range from around $12 to $1,300 for the best seats at the opening ceremony.
The Rio 2016 Games, the first Olympics to be held in South America, will be held from August 5 to 21.