TORONTO -- Two people are dead and three others are in hospital following an overnight shooting that began inside a packed Toronto nightclub hosting the official after-party of rapper Drake's annual OVO Fest.

Two people were killed and three others were injured after shots were fired early Tuesday at the Muzik nightclub, where thousands of people were partying. The area around the club already had a heavy police presence due to the size of the crowd.

 "This was a brazen, large-scale ongoing firearm incident and our officers and members of the public were directly in the line of fire," said Deputy Police Chief Peter Sloly. "We were very lucky that this was not a larger body count, quite frankly."

Sloly said officers responded to a call about shots being fired inside the nightclub at about 3:15 a.m.

As officers were rushing into the club where they encountered a "crush of people" fleeing the scene, a second series of gunshots was heard from an area north of the venue, police said.

The first officer to arrive at that area found a woman who had been shot and was able to administer CPR before she was rushed to a hospital where she died, police said.

Inside the nightclub, police found one man who died after being shot on an outdoor patio.

Another man and a woman were found injured with gunshot wounds at the club, while a third man was found with a gunshot wound several blocks north of the venue after he flagged down an ambulance, police said.

Hours later, police said they wanted to speak with two persons of interest.

One of them was believed to be related to the scene inside the nightclub and was described as a black man between 25 to 26 years of age, about six feet in height with a fresh buzz cut, wearing a light purple crew neck sweater with a colourful design on the front and dark blue jeans.

The second man, who was related to the scene north of the club, was described as a brown man with a skinny build, aged 24 to 28 years, about 5-10, wearing a yellow and burgundy plaid button up shirt.

Police asked for the public's help identifying the two men and asked for witnesses to share their accounts of what had happened in and around the club. They also asked anyone with photos or video from any point in the night to share their footage with police.

"Five people were shot today and that's just unacceptable," said Insp. Peter Moreira.

"This is a cowardly act where the perpetrators rely upon the fear and silence of a great number of people there to continue to lead this kind of life and that concerns us. It's something our investigators are well aware of. We understand the need to get to the bottom of this, that's why we're making this appeal."

The nightclub was hosting the official OVO Fest after-party featuring Toronto rapper Drake.

Representatives for Drake didn't immediately respond to messages seeking comment and police wouldn't say whether the musician was at the nightclub at the time of the shooting.

Toronto Police Supt. Frank Bergen said the victims of Tuesday's shooting were in their 20s and 30s.

He said the organizers of the "well-run event" were doing their best and the incident happened as they were shutting down for the evening.

In a statement, Muzik said it had "73 professionally trained" security guards on duty, which included "15 specially trained guards who conduct body searches, including the use of metal-detecting wands, on all patrons entering the property."

The club said it also had 10 armed Toronto police officers on paid duty as part of the security detail.

Muzik's owner, Zlatko Starkovski, said the club is co-operating with police and has "full confidence they will get to the bottom of this horrific incident and bring these people to justice."

Police said it was unclear how a gun got into the club with such tight security and so many officers outside, but noted that the large area also has a pool that is surrounded by a fence, but "is not airtight."

A similar incident occurred in front of Muzik after OVO Fest last summer when a 28-year-old man was shot and suffered serious injuries.

With files from Matt Ingram and Diana Mehta.