Stefanos Tsitsipas says he did not mean to hit his dad with his racquet when he lost his temper during his ATP Cup defeat by Australia's Nick Kyrgios.

The Greek, 21, smashed his racquet twice near the team bench after losing a first-set tie-break, catching his dad Apostolos' arm with the second swipe.

Apostolos, also his son's coach, looked stunned and went to sit in the stands, clutching his bruised right arm.

Stefanos, meanwhile, was warned by the umpire and then told off by his mum.

"It happened accidentally. I didn't mean to do it and straight away forgot about it and moved on from there," Tsitsipas told reporters after the 7-6 (9-7) 6-7 (3-7) 7-6 (7-5) loss in Brisbane.

"It happens, I wasn't aiming to do that. It just went out of control, unfortunately.

"Maybe I'll stay in my room for three days, grounded by my father," he joked.

Mum Julia, a former professional tennis player, came down from the stands to lean over the barriers and give her son a telling-off.

Tsitsipas was later docked a point for unsportsmanlike behaviour after smashing a ball towards his team bench.

Kyrgios, who is no stranger to on-court meltdowns himself and is serving a six-month probationary period as part of a suspended 16-week ban for "aggravated behaviour", played down the incidents.

"I've done some stupid things as well in the heat of the moment, so it was obviously an accident," he said after Australia's 3-0 victory in the tie.

Hosts Australia play Great Britain in the quarter-finals of the inaugural ATP Cup in Sydney on Thursday (starts 23:00 GMT Wednesday).