HONG KONG (AP) — Hong Kong police announced Saturday they have arrested four men in connection with two apparent gasoline bomb attacks on law enforcement.

The arson cases occurred Friday, first near a police vehicle and then by a police station, said the Hong Kong government.

The attacks come as police brace for what is expected to be a major protest Sunday against proposed changes to Hong Kong's extradition law that would allow some suspects to be sent to mainland China to face charges.

In the early hours of Friday, officers inside a patrolling police vehicle spotted a man holding an ignited glass bottle that he then threw toward the car before fleeing. In the afternoon, a man threw an ignited glass bottle toward the wall of a police station. It landed on the ground and erupted into flames.

The four men taken into custody are between the ages of 22 and 60, and the police may still make more arrests, according to the Hong Kong government.

No one was reported injured in either incident.

The extradition law amendments have been widely criticized as eroding the semi-autonomous Chinese territory's judicial independence.

Under its "one country, two systems" framework, Hong Kong was guaranteed the right to retain its own social, legal and political systems for 50 years following its handover from British to Chinese rule in 1997. However, China's ruling Communist Party has been seen as increasingly reneging on that agreement by forcing through unpopular legal changes.