HONG KONG - A Hong Kong anti-government activist was arrested by police, his organization said on Monday, after a protest he helped organize in the financial district a day earlier turned violent with officers firing tear gas to disperse the crowds.

Ventus Lau was arrested on Sunday evening on charges of "obstruction of police administration" and violating terms set when permission was granted for the protest, the Hong Kong Civil Assembly Team said in a statement.

The organizers initially applied for a permit - known as a letter of no objection - for a march, but police only agreed to a static rally in a park in the city's Central district.

But as the crowds swelled and spilled onto surrounding streets, some protesters briefly barricaded roads with umbrellas, traffic cones and other street furniture and dug up bricks from the pavement.

Police then ordered a halt to the rally and began dispersing the crowd. "It was primarily rioters' violent acts which led to the suspension of the gathering," Senior Superintendent Ng Lok-chun told reporters.

"The organizer has violated the agreements set in the no objection letter, failed to assist in maintaining the order in the public gathering event, that is why we have arrested Mr Lau."

Police said two community liaison officers were attacked with wooden sticks and sustained head injuries. They also said some protesters threw water bottles at officers conducting a "stop and search" operation.

In a statement late on Sunday, the government said it "strongly condemns" the attack on the police officers.

Hong Kong's junior police officers group condemned the organizer, Lau, as "irresponsible" and said his alleged abetment of the attack on two police officers liaising with him was despicable.

Lam Chi-wai, chairman of Junior Police Officers' Association, said in a statement on Monday that it was a person acquainted with the officers who had instigated the attacks.

These attacks have destroyed the trust between police liaison officers and residents, said Lam in the statement, adding that the rally organizer had been incapable of maintaining order.

In all, four officers were assaulted on Sunday and suffered head injuries and finger fractures. Two of them remained in hospital for treatment as of Monday noon, according to police.

With inputs from Jeffery Gu