The Oklahoma City Thunder needed a big fourth quarter performance to swing a seven-point deficit and beat the Indiana Pacers 111-104 to tie the NBA Finals best-of-seven series 2-2.

Frustrated for much of the game by Indiana's relentless defense, the NBA's Most Valuable Player, Shai Gilgeous-Alexander, found a way to fight through eventually in the fourth as desperation basketball saw them beat a thorough Pacers defensive setup that has been elite this campaign.

Gilgeous-Alexander followed a three-pointer with a pull-up jumper to give the Thunder their first lead since the first half with 2:23 remaining.

They wouldn't trail again, Gilgeous-Alexander adding six free throws in the final 44 seconds.

"It's a dog fight," Gilgeous-Alexander said after another intense, physical battle between the two teams.

"Every time you step on the floor, on both ends of the floor they make you work," he told AFP.

Jalen Williams added 27 points, Chet Holmgren added 14 points and 15 rebounds, while Alex Caruso chipped in 20 points off the bench for the Thunder.

Pascal Siakam scored 20 points to lead Indiana, adding eight rebounds, five assists, and five steals.

Playmaker Tyrese Haliburton scored 18 points and Obi Toppin added 17 off the bench as the Pacers led by 10 late in the third quarter, right before the Thunder came back into the match through Gilgeous-Alexander's strong performance.

"We knew it when we woke up this morning. 3-1 is a lot different than 2-2 going back home," Gilgeous-Alexander said.

"We played with desperation to the end of the game and that's why we won."

Gilgeous-Alexander said the Thunder must "maintain the same desperation" when they host game five on Monday. Game six will be held in Indianapolis, with a game seven if needed back in OKC.