The third period was filled with fights, and there was an accusation by Montreal's Max Pacioretty that Mikhail Grabovski bit him and also Colton Orr's apparent attempt to knee the Canadiens' Tomas Plekanec.
"We had a really great start to the hockey game," said Toronto coach Randy Carlyle, whose team completed a sweep of a three-game road trip and is 6-1-0 away from the Air Canada Centre including a season-opening 2-1 win in Montreal on Jan. 19.
"We did a lot of things in the first 10 minutes that kind of set the tone for our group for the rest of the night. We got the two-goal lead and then you know they're going to push back."
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The Canadiens answered with 20 shots in the second period, but couldn't beat Reimer who got his first shutout of the season and seventh of his career.
"This has been a good road trip for us," Reimer said. "We wanted to finish it off on a good note and the team worked hard and we were able to do that."
Tyler Bozak scored later in the first period, James van Riemsdyk and Phil Kessel added second-period goals and Korbinian Holzer and Dion Phaneuf, with his first of the season, scored in the third for Toronto.
"We weren't ready to start," Montreal defenseman Josh Gorges said. "Toronto, at home, in our building, and we're not ready to play? That's not good enough."
Pacioretty, who emerged from the melee showing his wrist to the officials, saying that Grabovski bit him. Both players were given 10-minute misconducts.
"That doesn't belong in our sport," Gorges said. "If you get in there, stand up for yourself, be a man, drop your gloves, and you'll have respect. But bite somebody? That doesn't belong in our league."
"I saw the bite," Montreal coach Michel Therrien said. "You can see that on the video. I'm sure the league's going to pay attention to that."
After Phaneuf scored during a two-man advantage at 13:15, more aggression broke out when Orr clipped Plekanec's leg, although the Canadiens center avoided a direct hit with a last-moment leap and was not injured.
Therrien said the NHL's disciplinarians should look at that incident as well, but Carlyle pinned the focus on Prust.
"We've got to take care of our own selves and we've got to look after business," he said. "And all the complaining that they want to do about it, the whole thing was started by what we felt was one player.
"Well, Prust, we know what kind of player he is and he goes out and cheap shots Grabovski. Well, what are we supposed to do? We're not supposed to play the rest of our players for the rest of the night? Well, they've got another thing coming. That's not happening to our group."
The Canadiens are 0-2-1 in their past three games and head south this week for games in Florida and Tampa Bay.
The game wasn't a minute old when Nikolai Kulemin tipped the puck past Andrei Markov at the blue line and the Montreal defenseman - coming off two knee surgeries - was unable to get back as Kamorov went to the net to tip in the pass on a 2-on-1 break.
It was the first goal in 12 NHL games for Kamorov, the first-year winger from Estonia.
The goal seemed to throw Montreal into disarray, and the Leafs capitalized as van Riemsdyk banked a puck off Carey Price to Bozak for a shot into an open side at 6:33.
Kessel put a move on the Montreal defense at the side of the net and passed to the onrushing van Riemsdyk for his seventh goal 3:36 into the second period.
Kessel got his second of the season and second in as many games on a power play as he picked the top corner from 15 feet at 18:01.
Holzer made it 5-0 four minutes into the third period before Phaneuf scored from the slot at 13:15.
Price let in all six goals and finished with 22 saves.
"They beat us with speed," Therrien said. "They were ready to play and we weren't. We got shots, but we didn't have any net presence."
- Komarov was moved onto a line with Mikhail Grabovski and Kulemin.
- Ryan White was a healthy scratch a game after taking a costly penalty in Thursday's shootout loss in Buffalo. Yannick Weber and Tomas Kaberle were also out for Montreal.
- Mike Komisarek was scratched for a fourth straight game for the Leafs and Dave Steckel didn't dress for a second game.