GREENSBORO, N.C. — Ty Lawson got back just in time for North Carolina, saving the top-seeded Tar Heels from a stunning NCAA tournament loss in their home state.

Lawson scored 21 of his 23 points after halftime, and his three-point play sparked the decisive second-half run as North Carolina held off LSU 84-70 in the South Regional on Saturday.

Wayne Ellington scored 23 points to lead the Tar Heels (30-4), who ran off 11 straight points in a tie game to take control and move on to next week's regional semifinals in Memphis, Tenn. North Carolina will face the winner of the Gonzaga-Western Kentucky game.

Marcus Thornton scored 25 points to lead the eighth-seeded Tigers (27-8), who gave the Tar Heels everything they could handle even while playing in front of a hostile crowd that was at least two-thirds full of light blue. But in the end, North Carolina — a veteran team trying to return to the Final Four — had just enough to hang on.

Lawson had missed the past three games after he jammed his right toe in practice two days before the regular-season finale against Duke. Coach Roy Williams had said the Atlantic Coast Conference player of the year had to get through practice Friday, experience no swelling later that night and get through pregame warmups to play.

It was apparent early on that the speedy junior was not 100 percent, but the longer the game went on, the better he got.

With the Tar Heels leading 64-63, Lawson split two defenders after a turnover and drew a foul while lobbing a shot to the rim. The ball hung there for a moment before dropping through, a three-point play that put North Carolina ahead 67-63.

Danny Green, who had an otherwise quiet game, followed with a 3-pointer before Lawson made another eye-popping move. This time, he lost Bo Spencer with a quick crossover dribble, drove into the paint and hit a double-pump hanging layup over the outstretched arm of 6-foot-11 Chris Johnson to push the lead to nine.

Tyler Hansbrough followed with a jumper to make it 74-63 with 4:45 left, a comfortable margin the Tar Heels would not relinquish.

Tasmin Mitchell finished with 18 points for LSU, which was making its first tournament appearance since reaching the Final Four in '06.

Lawson finished 7-for-13 from the floor to go with six assists and no turnovers in 31 minutes. The Tar Heels needed that big performance, too, considering Hansbrough managed only one second-half field goal before finishing with 15 points. He also needed treatment at one point for a small cut above his left eye during a scrap inside during a physical second half.

Green, who came in averaging 13 points, had just eight and was 2-for-9 before hitting his only 3 of the day during the big run.

Ellington also had a strong day, going 9-for-16 despite being defended much of the way by Garrett Temple, who had notably shut down national player of the year J.J. Redick during the Tigers' upset of Duke during his freshman year in 2006.

North Carolina shot 54 percent for the game, but also helped itself by dominating the boards for the final 13½ minutes. LSU held a 31-17 advantage on the boards at one point, but North Carolina started coming up with every critical one during the second half and ended up being outrebounded just 33-32 for the game.