A Hong Kong police officer has been hit by an arrow as authorities used tear gas and water cannons to try to drive back protesters occupying a university campus and surrounding streets.

Police said the arrow struck a media liaison officer, who was taken to a hospital. Photos on the department’s Facebook page show the arrow sticking out of the back of the officer’s lower leg.

An arrow sticks out of a police officer's leg
An arrow sticks out of a police officer’s leg (Hong Kong Police Dept. via AP)

Water cannon trucks drove over bricks and nails left by protesters and sprayed them at close range in a bid to drive them away on the streets outside Hong Kong Polytechnic University.

The push came in an hours-long stand-off that followed intense clashes the previous night.

A large group of people arrived in the morning to try to clean up the road, but were warned away by protesters.

Protesters shelter with umbrellas as an armoured police vehicle sprays them with water
Protesters shelter with umbrellas as an armoured police vehicle sprays them with water (AP/Achmad Ibrahim)

Riot police lined up a few hundred metres away and shot tear gas at the protesters, who sheltered behind a wall of umbrellas across an entire street and threw petrol bombs into nearby bushes and trees, setting them on fire.

The water cannons arrived in the early afternoon, one using blue-dyed water to drench the protesters.

The daytime face-off came after a battle at night in which the two sides exchanged tear gas and petrol bombs that left fires blazing in the street. Many protesters retreated inside the Polytechnic campus, where they have barricaded entrances and set up narrow access control points.

Police spray protesters with blue-dyed liquid
Police spray protesters with blue-dyed liquid (AP/Vincent Yu)

Protesters have largely retreated from occupations of several major campuses last week, except for a contingent at Hong Kong Polytechnic. That group is also blocking access to the nearby Cross-Harbour Tunnel, one of the three main road tunnels that link Hong Kong Island with the rest of the city.

Opposition politicians criticised the Chinese military late on Saturday for joining a clean-up to remove debris from streets near Hong Kong Baptist University.

Dozens of Chinese troops, dressed in shorts and 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.

Soldiers arrive to clean up the protest area at Hong Kong Baptist University
Soldiers arrive to clean up the protest area at Hong Kong Baptist University (Television Broadcasts Limited Hong Kong via AP)

The Education Bureau announced that school classes would be suspended again on Monday because of safety concerns.

The city’s anti-government protests have been raging for more than five months.

They were sparked by a government decision to submit 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 the UK 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 China, along with calls for full democracy for the territory.