HONG KONG >> Opponents of a proposed extradition law plan a protest Monday as Hong Kong marks the 22nd anniversary of the former British colony’s handover to China, and police said they were taking steps to prevent the possible disruption of a flag-raising ceremony.

Hundreds of thousands of people have filled Hong Kong streets to protest the measure seen as eroding the territory’s autonomy from Beijing. It would allow some suspects to be sent to mainland Chinese courts, which are controlled by the ruling Communist Party.

Organizers and police gave no estimate for possible turnout, but activists said some 2 million people, or more than one-quarter of Hong Kong’s population of 7.5 million, took part in a protest march in early June.

Hong Kong was promised a “high degree of autonomy” when colonial rule ended in 1997, but residents complain that is being eroded.

Opponents want the extradition legislation withdrawn and for Hong Kong’s chief executive, Carrie Lam, to step down, one of the protest organizers, Bonnie Leung of the group Civil Human Rights Front, said Saturday.

They also want an independent investigation into allegations of excessive force by police against protesters on June 12, Leung said at a news conference.

Leung said organizers obtained a police permit for the protest.

Officials speaking at a separate news conference said police were not “opposing parties” to the protesters.

“We are a partnership,” said a police official, San Tsz-kin. “We are here to assist them to facilitate them how to conduct a public event in a safe and orderly manner.”

However, San said authorities also are making preparations to prevent the possible disruption of a flag-raising to mark the day. The Chinese flag is raised each July 1 to commemorate the handover of the former colony.

Lam is due to attend the ceremony, the government said Saturday. It would be her first public appearance since she apologized on TV two weeks ago for mishandling the extradition legislation.

“Police have received information that someone will disturb the flag-raising ceremony,” said San. “We have made appropriate arrangements.”