BEIJING -- Only 450,000 tickets for this summer's Olympic Games have been successfully allocated, accounting for about a quarter of the tickets available for sale in the second phase, the Beijing Olympics Organizing Committee (BOCOG) said on Sunday.

More than 700,000 orders for 4.2 million tickets were received by BOCOG, but only 123,000 bookings were confirmed after a computerized random draw, BOCOG said in a notice posted on its website.

Though BOCOG didn't give a reason why about 75 percent of the tickets remain unsold, it is

 believed that it resulted from the fact that some popular events were extremely over-subscribed while the rest events had much less bookings.

The deputy head of BOCOG's ticketing center, said earlier that the demand was "extremely high but too centralized on several hot events".

A total of 1.8 million tickets to the sports events of the August 8-24 Games, together with 21,000 tickets for the opening ceremony of the Paralympic Games and 26,000 tickets for the closing ceremony, were put on sale in December.

More than 1.5 million tickets were allocated in the first stage of ticket sales last year.