Tickets for the Athens 2004 Olympics went on worldwide sale on Monday, with Greek organisers urging people to buy early to avoid disappointment weeks after sponsors snapped up all tickets allocated to them.

Athens organisers (ATHOC) said three million tickets were available, ranging from a single 11 euros ($12.74) seat to an "Olympic experience" package valued at 71,000 euros.

ATHOC ticketing manager Maria Manolopoulou declined to give specific figures but said interest on the first day was encouraging.

"Preliminary indications show a very high demand on tickets. National olympic committees have already requested a significantly higher amount of tickets than what was allocated to them for the Sydney Olympic Games." she said.

Government spokesman Telemachos Hytiris urged people not to leave applications to the last minute.

"It's still too early to say but you can be sure that there will be great demand for them so it is best to act now and book tickets early," he told reporters.

Average prices are about 35 euros, a reduction from 53 euros at the 2000 Sydney Games. More than two thirds of all tickets cost up to 30 euros.

Tickets for the most popular events such as swimming and athletics finals cost from 40-90 euros. A seat at the opening ceremony on August 13 starts at 100 euros and rises to 950.

Organisers say they have received four times as many applications for tickets to the opening ceremony as there are seats at the 70,000-capacity Olympic stadium.

ATHOC announced in April that all 2.3 million tickets set aside for national Olympic committees, TV rights holders, sponsors and other organisations associated with the 2004 Games had already been bought.

Despite delays in preparations and repeated reprimands from the International Olympic Committee to speed up work, ATHOC has been successful in marketing the Games, which are returning to the Greek capital after 108 years.

Hytiris said the Karaiskaki stadium would be in use for soccer though a re-building timetable was "borderline." The boxing arena would be ready for handover in February.