Police launched a late-night operation Sunday to try to flush about 200 protesters out of a university campus on a day of clashes in which an officer was hit in the leg with an arrow and massive barrages of tear gas and water cannons were fired.

Riot police began moving in on one group of protesters outside the campus after issuing an ultimatum for people to leave area. They used tear gas and water cannons on a resistant crowd wearing raincoats and carrying umbrellas.

Protesters used bows and arrows earlier in the day, and one arrow struck a media liaison officer in the calf. Photos on the department’s Facebook page show the arrow sticking out of the back of the officer’s leg through his pants.

As riot police moved in from all sides, some protesters retreated inside Hong Kong Polytechnic University while others set fires on bridges leading to it.

A huge blaze burned along much of a long footbridge that connects a train station to the campus over the approach to the Cross-Harbour Tunnel, a major road under Hong Kong’s harbor that has been blocked by the protesters for days.

The use of bows and arrows, along with a gasoline bombs launched with catapults, threatened to escalate the violence in the more than five-month-long anti-government movement. Protesters are trying to keep the pressure on Hong Kong leaders, who have rejected most of their demands.

The protests were sparked by proposed legislation that would have allowed the extradition of criminal suspects to the mainland. Activists saw it as an erosion of Hong Kong’s autonomy under the “one country, two systems” formula implemented in 1997, when Britain returned the territory to China.

The bill has been withdrawn, but the protests have expanded into a wider resistance movement against what is perceived as the growing control of Hong Kong by Communist China, along with calls for full democracy for the territory.

Several hundred people formed a human chain Sunday in central Hong Kong in a peaceful rally in support of the movement.

Azaze Chung, a university student, said the government should respond to the protesters’ demands, not just use force against them.

Police and protesters faced off all day outside Polytechnic after a pitched battle the previous night in which the two sides exchanged tear gas and gasoline bombs that left fires blazing in the street.

A large group of people arrived in the morning to try to clean up the road but were warned away by protesters. Riot police shot several volleys of tear gas at the protesters, who sheltered behind a wall of umbrellas and threw gasoline bombs into nearby bushes and trees, setting them on fire.

The protesters held their ground for most of the day, as water cannon trucks drove over bricks and nails strewn by protesters to spray them at close range — some with water dyed blue to help police identify protesters afterward.

Protesters began retreating into the university near sunset, fearing they would be trapped as police fired tear gas volleys and approached from other directions. The protesters have barricaded the entrances to the campus and set up narrow access control points.

They are the holdouts from larger groups that occupied several major campuses for much of last week.

Another group threw bricks in the street to block a main thoroughfare in the Mongkok district, as police fired tear gas to try to disperse them. The disruption to Nathan Road traffic may have been an attempt to distract police during the standoff at Polytechnic.

Opposition lawmakers criticized the Chinese military for joining a cleanup to remove debris from streets near Hong Kong Baptist University on Saturday.

Dozens of Chinese troops, dressed in black shorts and olive drab T-shirts, ran out in loose formation and picked up paving stones, rocks and other obstacles that had cluttered the street

The military is allowed to help maintain public order, but only at the request of the Hong Kong government. The government said that it had not requested the military’s assistance, describing it as a voluntary community activity.

The Education Bureau announced that classes from kindergarten to high school would be suspended again on Monday because of safety concerns. Classes have been canceled since Thursday, after the bureau came under criticism for not doing so earlier.

(AP)