A grizzly bear is on the loose after attacking a school group in Canada, leaving 11 people injured, two critically.

The incident happened on Thursday afternoon on a walking trail in the town of Bella Coola, British Columbia (BC). Residents have been warned to remain indoors while armed officers try to track down the animal. Four of the injured remain in the hospital as of Friday afternoon, BC's Health Services Authority has said.

A male teacher 'got the whole brunt of it,' and some children were hit with bear spray as the adults tried to fend off the animal, Veronica Schooner, a parent, told the Canadian Press.

Ms Schooner said her 10-year-old son was part of the school group, though he was not attacked. 'He said that bear ran so close to him, but it was going after somebody else,' she said, adding that 'he even felt its fur.'

In a statement to the BBC, British Columbia Emergency Health Services reported that two people were critically injured, two more were seriously hurt, and seven others were treated at the scene. Those injured had to be transported to a nearby airport for an airlift to the closest hospital.

The group was from Acwsalcta School, operated by the indigenous Nuxalk Nation, located 700km (435 miles) northwest of Vancouver. 'Officers are armed,' the Nation wrote on Facebook. 'Remain indoors and off the highway.'

'It's hard to know what to say during this very difficult time. We are so grateful for our team and our students,' they added. The school has been temporarily shut down, providing counseling services for the affected families.