'Threatened' fans demand apology from Kyrgios

A group of Israeli tennis fans given a mouthful by Nick Kyrgios insist they didn't provoke the fiery Australian and are demanding an apology.

Kyrgios took umbrage with opponent Dudi Sela's fans in his 3-6 6-3 6-3 win in Mexico on Wednesday.

During the second set, he paused prior to a second serve before telling a spectator to "shut the f--- up".

BIZARRE: Tomic quits due to 'unbearable' 27-degree heat

MOVING ON: Kyrgios through to third round in Mexico

After the match, the veteran Israeli confronted Kyrgios as the umpire stepped in between the pair.

Kyrgios and Sela argue after their match. Source: Tennis TV

The players appeared to resolve their differences with Sela patting Kyrgios on the shoulder and moving on.

19-year-old spectator Isaac Cherem has spoken out about the incident involving Kyrgios.

"It wasn't like we were talking in the points or when Kyrgios was serving; it was only cheering in between the points," Cherem told Fairfax.

"We were maybe three metres away from him, if we whispered, he could hear us.

"(My friend) whispered and then Kyrgios said shut the f*** up."

Cherem added he and his friends felt somewhat threatened.

"At first we were a little bit scared because he's a big dude.

"… I'm offended. He's a really, really good player, but he just doesn't have the head for the game."

It was an awful day for Aussie tennis, with Bernard Tomic also making headlines for all the wrong reasons.

He looked disinterested and lethargic before withdrawing from his first round match after losing the set in a tiebreaker.

Despite a relatively comfortable temperature of 27 degrees in Acapulco at the time, several reports quoted him as saying the heat was unbearable.

with AAP