ST. CATHARINES, Ont. -- Police were searching for two armed men Thursday following a daytime shooting in St. Catharines, Ont., that sent three people to hospital, two of them in life-threatening condition.

Niagara regional police said officers were looking at a number of residences in a downtown area of the city west of Toronto in what they described as a "slow, methodical process."

Const. Phil Gavin said Thursday night they were looking for two men, 19 to 23 years old, who were wearing hoodies and jeans.

"The full strength of the Niagara regional police is involved right now ... we're doing everything we can to resolve this situation safely for everyone involved," Gavin told a news conference.

He said investigators believe the shooting was a targeted incident.

Those injured in the shooting have not been publicly identified, but authorities said two have been flown to trauma centres in life-threatening condition while a third was taken to a local hospital with non-life-threatening injuries.

Gavin said police were called to the intersection of Church and Niagara streets at around 3:45 p.m. The nearby intersection of Queenston and Geneva streets was also affected, he said.

He said investigators were trying to figure out if the shootings occurred outside or inside a home.

Gavin said numerous officers, including the tactical unit, negotiators, the K-9 unit and emergency responders were all on the scene.

Police advised residents to stay out of the area, and employees of local businesses said they remained inside with doors locked until more information was available.

Coun. Mat Siscoe, who represents part of the area where the shooting took place, said the neighbourhood has struggled economically in recent years.

"The main hospital used to be just down the street from there, and it's been a fairly economically depressed area since the hospital closed down about four years ago," he said.

But he said such levels of violence are unusual in the neighbourhood.

"It's unusual for the city of St. Catharines in general," he said. "We're not used to gun violence in the city. Not on this scale."

Dan Peterson, who's lived in the area for more than a year, was among the dozen or so people waiting outside police lines Thursday night, barred from entering their homes.

He was turned away from the police tape at 5 p.m. and was still waiting to be allowed through four hours later.

"We're just waiting the situation out," he said, noting that others have tried to dart through the police tape.

Peterson said that while the neighbourhood isn't crime-free, he was surprised by the magnitude of the violence.

"You see little scraps here and there, but that's about it," he said. "That's child's play compared to what's going on now."