Khabib Nurmagomedov retained his lightweight belt at UFC 229 with a rear-naked choke of Conor McGregor in the fourth round, but the event ended in mayhem as further fighting broke out.

Having made McGregor tap out, Nurmagomedov initiated a mass confrontation by climbing out of the octagon and aggressively approaching McGregor's team member Dillon Danis.

Former lightweight champion McGregor then came under attack by two individuals who climbed into the octagon, marring what had been a dominant victory for the Russian.

Nurmagomedov took the Irishman – in his first UFC fight since November 2016 – down in the first round but did not do much more damage.

He really asserted himself in the second by wobbling McGregor with a haymaker before securing another takedown and raining a combination of punches and elbows down on his opponent.

McGregor got up with a slight swelling around his left eye, but it did not get rid of the token smile he has become so well known for.

In the third, McGregor stuffed two takedown attempts from Nurmagomedov, but the pair started trading punches and the Russian showed off some good technical jabs and worked in some combinations.

Nurmagomedov once again took down McGregor in the next section and finished him with a rear-naked choke with less than two minutes left in the round, taking his record to 27-0.

He then yelled at McGregor, went over the cage and into the crowd to spark the ugly scenes in the aftermath.

UFC president Dana White refused to present Nurmagomedov with his belt in the octagon, as the Russian followed McGregor in being escorted out of the main arena.