PITTSBURGH (Reuters) - The Montreal Canadiens eliminated the Stanley Cup champion Pittsburgh Penguins from the NHL playoffs on Wednesday and booked their first trip to Eastern Conference final in nearly 20 years.

Montreal will play the winner of Friday's decisive Game Seven between the Boston Bruins and Philadelphia Flyers, who stayed alive with a 2-1 victory on Wednesday in the night's other action.

The upstart Canadiens, who surprised the top-seed Washington Capitals in the first round, took the decisive seventh game 5-2 in Pittsburgh and dashed the Penguins' hopes of becoming the league's first repeat champion since 1998.

"They did a lot of good things that good teams need to do to win," said Pittsburgh captain Sidney Crosby, who had one goal in the series. "Unfortunately for us, we didn't do that."

Thousands of Canadiens fans, many who watched the game on big screens at the Bell Center in Montreal, raced onto nearby downtown streets to celebrate the improbable victory.

Brian Gionta scored twice for Montreal and young Slovakian goalie Jaroslav Halak made 37 saves as the team's post-season run continued.

After entering the playoffs as the Eastern Conference's lowest seed, Montreal erased a 3-1 series deficit to defeat Washington in the first round before knocking out a heavily-favored Penguins team that had led the series 3-2.

In the do-or-die contest, Montreal raced to a 4-0 advantage to silence the Pittsburgh crowd and chase starting goaltender Marc-Andre Fleury after just 13 shots.

Gionta put the visitors on top 32 seconds into the first period and Dominic Moore also scored for a 2-0 lead.

Michael Cammalleri, who leads all playoff goal scorers with 12, and Travis Moen padded the lead with goals in the second.

The Penguins fought back before the period ended with goals from Chris Kunitz and Jordan Staal, but Gionta sealed the win when he scored 10 minutes into the third.

"We might be changing some minds," Cammalleri said of the team's underdog tag. "We've had that underlying confidence. It's been good so far, but we have to get better."


Flyers goaltender Michael Leighton, who played in his first post-season game earlier this week after starter Brian Boucher was injured, made 30 saves in his latest appearance and held Boston scoreless until the game's final minute.

With the win, the Flyers erased Boston's 3-0 series and could become just the third team in NHL history to overcome such a deficit and win the series.

Mike Richards and Danny Briere put the Flyers up 2-0 before Boston's Milan Lucic scored with one minute to go.

Boston has not appeared in the Eastern Conference final since 1992 while Philadelphia last made it that far in 2008.

(Writing by Jahmal Corner in Los Angeles; Editing by Frank Pingue)