Paul Pierce scored 27 points and Kevin Garnett had 18 with 10 rebounds as Boston Celtics beat Los Angeles 92-86 on Sunday to put the reigning champions on the brink of defeat in the NBA finals.

Rajon Rondo had 18 points and eight assists for the Celtics, who defended their home court for the second straight game to take a 3-2 lead in the best-of-seven championship series.

Pierce shot 12-of-21 from the field as Boston put on a shooting clinic in front of a crowd of 18,624, hitting 56.3 per cent from the field to move within one victory of capturing their second championship in three years.

"I wanted to be aggressive from the jump," Pierce said.

"Coach ran the first play for me and I got a nice look and I wanted to continue throughout the game.

"My team-mates did a good job of finding me in the open and setting picks."

The series now shifts back to California, where the Celtics will try to win their NBA-leading 18th title in franchise history with a win in game six tomorrow at the Staples Center arena. A game seven would also be in Los Angeles.

"We have been one of best road teams all year and we are too close to our goal. We got to get one (more win)," Pierce said.

Kobe Bryant did his best to rally the troops, scoring 19 of his game high 38 points in the third quarter for the Lakers who became the first team in the series to lose two games in a row.

Spain's Pau Gasol finished with 12 points and 12 rebounds for the Lakers, who are not only vying for back-to-back titles but seeking a measure of revenge after losing to the Celtics in the finals two years ago.

Bryant didn't get much help from his team-mates as the Lakers shot just 39.7 per cent from the field.

Gasol had been averaging 20.1 points per game in the play-offs.