VANCOUVER (CP) _ An apparent gang shooting in Vancouver has prompted one of the largest police investigations in the city's history amid fears the brazen and deadly early morning attack could spark retaliation.

Two men were killed and six people injured early Thursday morning when two masked men burst into a Chinese restaurant and gunned them down, an attack that Vancouver police say bore all the hallmarks of a gang-related incident.

The 19-year-old and 26-year-old were known to police to have gang connections, though to which of the many organized crime groups roaming city streets police would not say.

``We are very concerned about a retaliation,'' Deputy Chief Doug Le Pard told reporters at a briefing on Friday morning.

``So we have our speciality members _ like in our gang crime unit and our criminal investigation section _ who are very much focused on doing what they can to diffuse any tensions that are out there and gather the intelligence so that we can move on this investigation as quickly as we can.''

Police released few details about the investigation on Friday, though officers clarified that three of the injured victims were male and three female. On Thursday, police had said four of the injured were female.

One of the victims, a 26-year-old male, remains in critical condition. A 22-year-old male and a 19-year-old female were listed in serious condition, and a 25-year-old male, 18-year-old female and a 19-year-old female were listed in stable condition.

All were from the Vancouver area of British Columbia, police said.

Police said they didn't know why the group had been at the Fortune Happiness restaurant, an all-night eatery that hadn't previously been on their radar as a hotspot for gang activity.

They also haven't revealed whether all nine members of the group, including one who escaped harm, had been the targets of the attackers who fled moments after the shooting.

Fears about a retaliatory attack aren't unfounded, said Prof. Neil Boyd, a criminologist from Simon Fraser University.

``It's a legitimate fear born out by the historical record,'' Boyd said in an interview.

``We've seen many cases of these kinds of violent attacks and responses from individuals, groups of individuals who have been targeted. The response might not come for a month, or two months or six months but often there is a response.''

Despite the massive police reaction, Chief Jamie Graham sought to calm any fears that a retaliation could catch innocent civilians in the cross-hairs, similar to gang-related incidents in Toronto that have left innocent bystanders _ including young children _ dead.

``We have some very talented people out there who are doing everything they can to assure the public is safe, they will do their very best to find these offenders,'' he said, in what was one of his final news conferences as Vancouver's chief of police.

``We have sources, we have contacts in various elements in Vancouver that our people are going to be beating the bushes to determine that kind of intelligence.''

Though bystanders have narrowly missed being caught in gang-related violence in other B.C. incidents, Boyd said the likelihood of bystander casualties is low.

``Your risks of being hurt are much greater if you go to bars, are much greater if you are out on the streets between 9 p.m. and 3 a.m.,'' he said.

Police reiterated Friday that part of the gang problem in Vancouver is linked to a steady flow of illegal guns coming up from the United States. Graham said 300 firearms were seized in the last year in Vancouver, including three silencers found on loaded weapons.

``These aren't throwaway Saturday night specials, these are good solid quality handguns that we seize,'' he said.

``This isn't Vancouver of the '50s, Vancouver right now faces a gun problem and we are doing our best.''

© 2007 The Canadian Press