World number five Andrey Rublev was sensationally defaulted after being accused of swearing at a line judge in the deciding set of his semi-final at the Dubai Open.

The combustible Russian was trailing 6-5 in the third against Alexander Bublik when he appeared to say something to the line judge.

ATP supervisor Roland Herfel came down to the court accompanied by a Russian speaker, who claimed Rublev had sworn in his native language.

Rublev protested, insisting he was speaking in English, while Bublik also backed his opponent.

“I didn’t say ‘f******’. I swear to God. This is huge. I swear to God,” said Rublev.

The offence would usually merit a warning in the first instance, but the 26-year-old was defaulted by umpire Miriam Bley amid jeers from the crowd in Dubai.

It was a controversial end to a tight match, with Kazakhstan’s Bublik progressing to the final 6-7 (4) 7-6 (5) 6-5.