Generally speaking, yelling "add oil" in a stadium would be fine, though, Yeung added.

Speaking on a radio program on Saturday, Yeung said people should never express political messages through sports, one of the principals of the International Olympic Committee, which applied to other sports events as well.

However, he said he could not define political elements then and there, and it depends on people's motives and what messages they are trying to spread. The National Sports Association may seek advice from law enforcement, when necessary, he continued.

It will be okay to chant the words "add oil" in general, a Cantonese slang phrase which means "keep it up," Yeung said.

The use of the term had previously caused controversy as activists and protesters chanted the Cantonese slogan "Hong Kong add oil!" during the social unrest. Supporters from the pro-establishment camp have accused people who chant this slogan at sporting events of advocating their political stance.

In October, runners at the Hong Kong Marathon were stopped at the starting line and were told to change their clothes with logos or slogans that said "Hong Kong add oil" before joining the race.

A man who tattooed the slogan "Hong Kong add oil" on his leg was asked to cover it with a bandage.

Yeung, on another note, defended the decision to postpone the Hong Kong Sevens again to November 2022, saying that the physical contact of the game challenges the anti-pandemic measures, and the tournament can hardly be staged within a short period.

Holding closed-door games is not practical either, he added.

He pointed out that there are too many players to handle, and holding closed-door games will increase the financial burden of the Hong Kong Rugby Union, as the sales of the admission tickets and consumption of food and drink in the stadium are their primary sources of income.