By Steve Keating

BOSTON (Reuters) - Vancouver Canucks defenseman Aaron Rome has been banned from playing in the rest of the Stanley Cup finals after his late hit on Boston Bruins forward Nathan Horton left his opponent severely concussed and also out of the series.

Rome apologized to Horton after he flattened him during the opening period of Monday's third game, won 8-1 by the Bruins, but the National Hockey League (NHL), under increasing pressure to clamp down on violence in the sport, took a dim view of his actions.

He was handed a maximum four game suspension, a record ban for a player in the Stanley Cup finals. If the series ends before game seven, the suspension will carry over into next season.

"I thought it was a late hit," NHL Senior Vice President of Hockey Operations Mike Murphy told reporters.

Horton, who had been one of Boston's best players during the playoffs, was sent crashing to the ice when Rome struck him after he had passed the puck.

The game was stopped as medical staff raced to his help, carefully strapping the motionless Horton onto a stretcher then transporting him to a local hospital where he was examined and kept overnight.

Horton was released on Tuesday but the Bruins said he would not be able to play in the rest of the finals and would likely be replaced by rookie Tyler Seguin. The Canucks lead the best-of-seven series 2-1 with game four in Boston on Wednesday.

"We're concerned about Nathan's health, that's our priority," said Bruins forward Gregory Campbell. "You play this game to win, not to hurt other people.

"This is the Stanley Cup finals and the intensity is extremely high and as players you have to play on the edge but you have to make sure you're playing within the rules."

The Canucks released a statement from Rome saying that he had not intentionally tried to hurt Horton.

"I want to express my concern for Nathan's well being and wish him a quick and full recovery, I try to play this game honestly and with integrity," the statement read.

"As someone who has experienced this type of injury I am well aware of its serious nature and have no desire for another player to experience it."

Murphy said the decision to suspend Rome was not made lightly but Canucks coach Alain Vigneault took issue with the league, saying the suspension was too harsh.

"We're real disappointed the player got hurt but it was a north/south play," Vigneault told reporters.

Boston coach Claude Julien said he supported the decision to suspend Rome after the Bruins had been hard hit by concussion injuries this season.

Center Marc Savard was ruled out of the finals after being concussed for the second time in less than a year and Patrice Bergeron missed two games of the Eastern Conference final after he showed symptoms of concussion.

"We need to clean up those kinds of hits," Bergeron said. "There's no easy decision. This is a contact sport.

"You can't take the contact out of the game. Just got to try to take those situations where it becomes extremely dangerous out of the game."

(Editing by Julian Linden)