TORONTO - Toronto police say they will launch a criminal investigation into allegations an officer fired rubber bullets that injured a G20 protester outside a detention centre.

Police spokesman Mark Pugash said Friday the probe will examine all the circumstances around allegations made by a Montreal woman, who says she was injured by two such bullets last June 27.

Natalie Gray, 20, is suing Toronto police, alleging she was struck in her left arm and sternum by the rubber bullets while she and about 150 others held a peaceful protest outside the temporary detention centre.

"We've said from the beginning that any information takes us closer to the truth we would welcome and that applies in this case," Pugash said.

"We will follow the evidence where it goes."

Gray's lawyer Clayton Ruby called for criminal charges in the case during a news conference at his Toronto office Friday. Ruby said the officer who fired on Gray should be charged with assault and unlawful use of a firearm, which carries a 10-year maximum term.

Pugash confirmed police Chief Bill Blair has received a letter from Ruby demanding an investigation.

Ruby, who also called for a full public inquiry into police actions during the summit, said he provided the chief with a photograph of an officer firing a gun and video taken by a bystander.

"That officer is clearly identifiable, he should be charged with a crime," he said.

Gray launched a lawsuit in September against the Toronto Police Services Board and 10 unidentified officers. Police filed a statement of defence last week, denying the claims. The allegations have not been proven in court.

In her statement of claim, Gray alleges assault and battery, unlawful arrest and detention and violation of her constitutional rights. She is seeking more than $1.6 million in damages.

Photographs provided by Gray show a round, red circle with a large red blotch on the back of her left arm and bruising around her elbow.

Speaking on the telephone from Montreal to reporters in Toronto, Gray said being shot with rubber bullets was painful. Afterwards, she was shoved to the ground and screamed at before being put in a cruiser, she said.

"I was the most terrified I've ever been," said Gray, who suffers from asthma.

She said she asked to see a doctor but wasn't allowed to for a half-hour. When she complained, a senior officer told her to "suck it up," she said.

While her physical wounds are mostly healed, Gray said she's seeing a psychologist to deal with the trauma.

"I guess I feel mostly frustration -- frustration that officers can do something like this," said Gray.

A charge of obstructing a peace officer was laid against Gray but was dropped in August.

Her lawsuit is one of several launched in the aftermath of the G20 summit, when police detained more than 1,000 people after protesters smashed windows and burned police cruisers.