Alexander Zverev and Arthur Fils in heated exchange over underarm serve at Hamburg Open

The two were contesting the final when the Frenchman played an underarm serve that was booed by the crowd

Alexander Zverev looks on in dejection after losing to Arthur Fils in Hamburg (AP)

Alexander Zverev and Arthur Fils played out a tense, dramatic final at the Hamburg Open as the two clashed after an attempted underarm serve from the Frenchman.

Zverev, who is the world No 4 and was born in Hamburg, was attempting to win back-to-back titles in his home city, but fell behind to the 20-year-old Frenchman in the first set.

He fought back to win the second set 6-3, but the controversial moment came in the deciding set, with the scores tied at 5-5. Fils found himself a break point down, and played a disguised underarm serve that landed out.

Although it didn’t win the Frenchman the point, Zverev was angered and the home crowd booed Fils. At the changeover, the pair shared a few words, with Zverev allegedly accusing Fils of having “no respect”, and the umpire had to separate the players.

The Frenchman worked the crowd by pointing to his ear, shrugging and shaking his head, and he went on to win the final set 7-6 after a 7-1 tiebreak, lifting his first ATP 500 title.

After the final point, the pair exchanged a frosty handshake, with Fils looking bemused as an irritated Zverev barely made eye contact, muttered some words to himself and then proceeded to share a few argumentative words with the umpire.

Nevertheless, things seemed to have calmed down by the time the trophy was presented to Fils, with both players smiling as Zverev sprayed the Frenchman with champagne.

And Fils defended his actions shortly after winning, saying that he “did everything to win this match”.

“I got cramps at 5-5 in the third. I’m cramping, trying underarm serves because I cannot serve”, he said.

While the win in Hamburg caps off a good few weeks for Fils – who will be one of the main home hopes as the Olympics begins later this month – the result is the latest in a disappointing few weeks on the court for Zverev, who was beaten by American Taylor Fritz in the last 16 at Wimbledon.