NBA Most Valuable Player Shai Gilgeous-Alexander scored 29 points to seal an emphatic win against a Pacers side who lost talisman Tyrese Haliburton to a first-quarter injury.

The NBA championship was the first won by the Thunder since the franchise relocated to Oklahoma City in 2008. Their only other title came in 1979 when the team were the Seattle Supersonics.

Indiana had taken the best-of-seven series to a decider with a battling victory in game six last Thursday, when Haliburton fought through a calf strain to inspire a 108-91 win.

That left the Pacers needing to reproduce a repeat of their game one win on the road at top seeds Oklahoma City to clinch their own maiden NBA title.

But the scale of the task before the Pacers became even more daunting after Haliburton crumpled to the Paycom Center court in agony in the first quarter before limping out of the game.

The Pacers said Haliburton had suffered a "lower right leg injury", although ESPN cited the player's father as saying his son had suffered an Achilles injury.

Although the Pacers battled bravely to lead 48-47 at half-time, the Thunder pulled away, outscoring Indiana 34-20 to open up a hefty 13-point lead heading into the final quarter.

The Thunder were in no mood to let that advantage slip and they led by as many as 22 points in the fourth quarter before holding on to win.