Riot police form a line as they check pedestrians gathered in the Central district of Hong Kong, Wednesday, May 27, 2020. Hong Kong police massed outside the legislature complex Wednesday, ahead of debate on a bill that would criminalize abuse of the Chinese national anthem in the semi-autonomous city. (AP Photo/Vincent Yu)

HONG KONG (AP) — Thousands of protesters shouted pro-democracy slogans and insults at police in Hong Kong before lawmakers later today debate a bill criminalizing abuse of the Chinese national anthem in the semi-autonomous city.

Police massed outside the legislative building ahead of the meeting and warned protesters that if they did not disperse, they could be prosecuted.

In the Central business district, police raised flags warning protesters to disperse, before they shot pepper balls at protesters and searched several people. More than 50 people in the Causeway Bay shopping district were rounded up and made to sit outside a shopping mall, while riot police patrolled and warned journalists to stop filming while brandishing pepper spray.

At least 16 people, most of them teenagers, were arrested on charges of possessing items fit for unlawful purposes, such as petrol bombs and screwdrivers.

Three of the people arrested were charged for dangerous driving.

Lawmakers were to debate a bill that would make it illegal to insult or abuse the “March of the Volunteers” in the semi-autonomous Chinese city. Those found guilty could face up to three years in prison and a maximum fine of HK$50,000 (US$6,450).

The bill was proposed in January 2019 after Hong Kong spectators jeered at the anthem during high-profile, international soccer matches in 2015. Last year, FIFA fined the Hong Kong Football Association after fans booed the Chinese national anthem at a World Cup qualifying game.

Hong Kong was returned to China from British colonial rule in 1997 under a “one country, two systems” framework that promised freedoms not found on the mainland. Anti-China sentiment has risen as residents see Beijing moving to erode those rights.

Mass protests in 2014, known as the Umbrella Revolution, followed the Chinese government’s decision to allow direct election of the city leader only after it screened candidates. In the end, the plan for direct elections was dropped.

Legislation proposed in Hong Kong last year that would have allowed Hong Kong residents to be sent to mainland China for trials set off months of demonstrations that at times involved clashes between protesters and police.

The legislation was withdrawn.