A new law that punishes disrespect for China's national anthem with up to three years' imprisonment may also apply to Hong Kong and Macau, state media reported Tuesday.
The move could trigger a major backlash in semi-autonomous Hong Kong, which enjoys rights and freedoms not seen on the mainland under a "One country, two systems" formula.
Some football fans in the southern city have booed the anthem when it is played at matches, despite appeals for restraint.
China has been fine-tuning legislation on the proper way and place to sing its national anthem, recently tightening rules that already bar people from performing it at parties, weddings and funerals.
The country in September passed a National Anthem Law applying to mainland citizens, which specified a much lesser jail term of 15 days for disrespecting the song.
Under the new measures "punishment ranges from removal of political rights and public surveillance to criminal detention and imprisonment of up to three years", said the state news agency Xinhua.
China's legislature was this week deliberating the new measures and mulling whether to apply the law in Hong Kong and Macau, it added, without explaining why the penalty could increase so significantly.
The move could prompt major protests in the former British colony, which returned to Chinese rule in 1997 under a promise that rights and freedoms would be protected for 50 years.
"In recent years, incidents of disrespecting the national anthem had occurred in Hong Kong, challenging the bottom line of the principle of 'One country, two systems' and social morality and triggering rage among Chinese," Xinhua cited Zhang Rongshun as saying.
"It is urgent and important to apply the national anthem law in Hong Kong, in a bid to prevent and handle such offences," said the deputy director of the National People's Congress' legislative affairs commission.
Some Hong Kong fans booed and turned their backs during the playing of the "March of the Volunteers" anthem at a football match against Malaysia in October, despite appeals by football authorities.
There were also similar incidents at previous matches.
In 2015 during the World Cup qualifier between the city and its mainland rivals, Hong Kong fans jeered the anthem.
The match followed pro-democracy protests in late 2014, which gripped the city and underlined discontent with Beijing's rule.
Amnesty International China researcher William Nee told AFP the anthem move "would clearly be out of step with international law".
"Besides being incompatible with the right to freedom of expression to begin with, extending the law to Hong Kong and Macau is also especially worrying," he said.
"It could be the first step in chipping away at internationally recognized human rights, using mainland China's nearly limitless and vague concept of national security -- which is often used to suppress peaceful expression of ideas and shield the Communist Party from scrutiny."
An ideological push has intensified in China since President Xi Jinping took power in 2012. The leader has stressed a drive to infuse every aspect of Chinese education with "patriotic spirit".
Before Xi, China had laws covering the use of its national flag and national emblem but none for its anthem, aside from a ban on its use in advertisements.
Regulations adopted in 2014 allowed the national anthem to be played only during formal diplomatic occasions, major sporting events and international gatherings -- making the song off-limits at weddings, funerals and various forms of "private entertainment".