TORONTO  — Jon Jones successfully defended his light heavyweight title, surviving an early scare to submit former champion Vitor Belfort in the fourth round at UFC 152 on Saturday night.

Belfort came close with an armbar in the first round, but Jones’ reach, varied attack and ground and pound took a toll on the veteran challenger.

Unable to get his striking game going, Belfort tried to take the fight to the ground where he could use his jiu-jitsu. But he paid a price and finally fell victim to an Americana submission 54 seconds into the round. Jones improved to 17-1, and Belfort dropped to 21-10.

In the co-main event at the Air Canada Centre, Demetrious Johnson won a split decision – 48-47, 47-48, 49-46 – over Joseph Benavidez to become the UFC’s first flyweight champion.

Jones took down Belfort down 30 seconds after the opening bell, and the Brazilian responded with an armbar attempt that looked dangerous. Jones slammed Belfort down to the canvas and eventually wriggled free as the crowd began to chant “Vitor! Vitor!”

“I’ve never had my arm pop like that before,” said Jones, who said he would have let his arm break rather than tap out.

Jones remained on top and began to throw elbows, cutting Belfort. The doctor had a look at the battered challenger between rounds.

Belfort, who does his best work traditionally in the first round, came out punching in the second. But he had a hard time penetrating Jones’ reach. The champion began to pick away at Belfort, who pulled guard later in the round to bring the fight back to the ground.