Around 500,000 tickets for events at the London 2012 Olympic Games have been released for general sale, organisers Locog have said.
There are some £20 tickets left for sports such as volleyball, table tennis, weightlifting, taekwondo, boxing and fencing.
But several sports have sold out, and there are only higher-priced tickets left for most medal events.
The tickets went on sale at 11:00 BST, with a 24-hour window for purchases.
Their availability can already be viewed on the 2012 ticketing website.
Organisers Locog say there is a good number of tickets at the cost of £45 to £450 in sports including archery, badminton, basketball, beach volleyball, canoe sprint, diving, handball and hockey.
Only a limited number of tickets are available in race walk, mountain biking, artistic gymnastics and rowing.
Up to four tickets can be purchased per session, and up to four sessions in one transaction, for all available sports apart from football - where more tickets are available to encourage groups to attend.
'Delivered on promise'All tickets have been sold in some sports, including athletics, cycling, equestrianism, rhythmic gymnastics and swimming as well as the opening and closing ceremonies.
Locog commercial director Chris Townsend said: "Our priority has been to get as many people who missed out in the sales process last year to the Games.
"We have delivered on our promise and now another 150,000 people have successfully purchased up to four tickets each."
He warned: "Wednesday's sale is a live sale, and, like other high demand events including pop concerts, we expect the website to be very busy and customers may well be held in queues for over 30 minutes at peak times".
The online ticketing system sparked criticism last year after it crashed under high demand.
In some cases, the system reportedly informed potential buyers they had secured tickets, who were later told that they had failed.
Meanwhile, plans have been unveiled for a 10,000-spectator area with a giant screen showing live events in the Olympic Park during the Games.
"Park Live" will be open from early morning until late evening for fans without tickets for the sport venues.
Source: www.bbc.co.uk
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