LONDON - Olympic organizers say 1.8 million people have applied for more than 20 million tickets for the 2012 London Games.

In a six-week sale period until early Wednesday morning, 6.6 million tickets were made available online.

Organizers said in a statement that more than half of the 650 sessions across 26 sports have been oversubscribed and tickets will be allocated through a ballot, or lottery, system.

The first completely sold out events are the opening and closing ceremonies, track cycling, rhythmic gymnastics, triathlon, modern pentathlon and the cross-country equestrian competition.

Most of the swimming and tennis sessions have also sold out.

Organizers did not disclose how many tickets remain unsold, but said there will be further sales in June and July.