The government says people attending the opening ceremony for Kai Tak Sports Park on Saturday evening must get their tickets by 3pm on the day.

Some 8,000 people received vouchers which have to be exchanged in person for the tickets they bought.

Sports Commissioner George Choi said on Friday morning that so far, nearly half of the buyers have collected their tickets.

He said while the ceremony will begin at 6.30pm, the 3pm cut-off time for ticket exchanges is necessary for the sake of crowd control.

"Our gates will open at 4.30pm for the opening ceremony," Choi said at a press conference.

"If there are many people queuing for ticket exchange at the last minute, we don't want so many people colliding, going in different directions at the same time."

In total, more than 30,000 people are expected to attend the ceremony in the Kai Tak Stadium, with officials urging them to travel to the venue by public transport.

Choi said no parking will be available at the Kai Tak Mall inside the sports park on Saturday, a restriction that will also be in place for future large-scale events there.

There will be a special pick-up and drop-off zone on Sung Wong Toi Road for those arriving by private car or taxi.

Officials noted that no professional cameras, long umbrellas or water bottles will be allowed in the stadium, also reminding people that ticket scalping is not permitted.