Top seed Grigor Dimitrov was stunned in the first round of the Dubai Tennis Championships as Malek Jaziri came from behind to claim a shock win.

A procession may have looked in the offing when Dimitrov won the first set, but Jaziri produced a remarkable comeback to earn his first victory over a top-10 opponent.

The Tunisian saved seven of the eight break points he faced to emerge victorious 4-6 7-5 6-4 after two hours and 17 minutes.

World number four and reigning ATP Finals champion Dimitrov said: "You have days like this that you can't really do much else. Unfortunately, I couldn't play my game to the extent that I was looking for.

"My movement was not good over the court. I thought I served okay for a little bit, but then I lost my rhythm again.

"All the credit to Malek. He played a good game. He was strong throughout the whole match. Actually was hitting pretty good shots. I mean, [he had] nothing to lose."

Jaziri, who last beat a top-100 opponent 11 months ago, said: "[It is a] great feeling, to win my first [match against a] top-five player.

"I am really happy for that. I tried to fight every point since the beginning. It was so tight.

"I was really aggressive. I tried hard to keep the ball in, tried hard to attack him, to add a lot of variety in the game."

Dimitrov was not the only seed to fall at the first hurdle, with fifth seed Richard Gasquet beaten 6-4 6-3 by Borna Coric.

Second seed Lucas Pouille had no such issues in a 6-4 6-4 triumph against Ernests Gulbis, while fourth seed Damir Dzhumur was a comfortable 6-3 6-4 winner over qualifier Yannick Maden.

Eighth seed Yuichi Sugita defeated Ilya Ivashka 7-5 6-1 but Filip Krajinovic had to recover from an opening-set bagel to beat Thomas Fabbiano 0-6 6-2 6-2.

Pierre Hugues-Herbert overcame Joao Sousa in a match that went the distance and Karen Khachanov got the better of Denis Istomin in two tie-breaks.

Elsewhere in the draw there were wins for Evgeny Donskoy and Jan-Lennard Struff.