(REUTERS) - DeMar DeRozan scored 34 points to lead the Toronto Raptors to a 115-109 victory over the Boston Celtics on Wednesday, with the home team extending their winning streak to a season-best six games.

Centre Jonas Valanciunas added 19 points and 12 rebounds for the Raptors, who improved to 27-15 with the triumph against a tenacious Celtics.

Boston forward Jae Crowder cut the Raptors' lead to two points late in the game but guard DeRozan came right back with a 19-foot pull-up jumper to restore Toronto's advantage to four points with 46.9 seconds remaining.

After a Boston miss, Toronto point guard Kyle Lowry made two free throws with 14.8 seconds on the clock to clinch the game.

Forward Luis Scola scored 18 points for Toronto, forward Terrence Ross contributed 14, and Lowry scored 14 points and had eight assists.

Guard Isaiah Thomas scored 21 points and had 10 assists for the Celtics, who lost their second game in a row.

Guard Avery Bradley added 19 points, forward Kelly Olynyk had 18, Crowder 17 and guard/forward Evan Turner 11 for Boston (22-21).

Both teams shot well from the floor - 55.4 per cent for Toronto and 50.6 per cent for Boston.

The Raptors opened an early 13-point cushion and led 35-27 at the end of the first quarter thanks to 11 points from Scola and 10 from DeRozan.

The Celtics went on a 9-0 run late in the second quarter to storm into a six-point advantage, however, with Boston starting the second half 62-56 up, led by Crowder's 12 first-half points. Scola led all first-half scorers with 15 points.

The Raptors regained the lead, 70-68, on a three-pointer by Lowry with 7min 59sec to play in the third quarter.

There were five lead changes and six ties in the quarter before Valanciunas gave Toronto a five-point lead on a cutting lay-up with 1:24 left in the third.

DeRozan's turnaround jumper bumped the lead to seven points. Toronto led 96-90 after the three quarters.

Thomas cut the lead to two points on a jumper with 6:39 left, but DeRozan and forward Patrick Patterson scored to boost the Raptors' lead to six points.

A running lay-up by Thomas reduced the lead to two points. After a Raptors miss, Bradley tied the game at 105-105 on a 19-foot pull-up jumper with 3:20 to play.

Lowry responded with a three-pointer. After Olynyk scored for Boston, Ross hit a three-pointer and Toronto led 111-107 with 2:16 to go.