At least 10 people have died and 25 others are in hospital after a bus crash in Australia's wine region.

Emergency services were called to Wine County Drive in Hunter Valley, New South Wales (NSW) on Sunday, after reports a coach had rolled over.

The driver of the bus, a 58-year-old man, is under arrest at Cessnock police station.

The bus is believed to have been returning from a wedding at a nearby wine estate.

The Hunter region is known for its vineyards and native bushland, making it a popular spot for wine tourists and group outings.

NSW Police Acting Assistant Commissioner Tracy Chapman said the guests were travelling to Singleton "presumably for their accommodation".

She said two of the 25 people injured had been airlifted to hospital.

The number of fatalities could increase as the bus is still on its side and people could be trapped underneath, Ms Chapman said.

Police investigating the circumstances surrounding the crash say the crime scene is being examined by specialist forensic police.

Ms Chapman said there was "sufficient information" to charge the driver.

"He's under arrest. He's been the driver of a motor vehicle collision where there have been fatal injuries and there will be charges pending," she said.

Australian Prime Minister Anthony Albanese sent his condolences to the loved ones of those killed in the "horrific" tragedy.

"For a day of joy to end in such devastating loss is cruel indeed. Our thoughts are also with those who have been injured," he said.

A wedding guest said the day had been a "fairy tale" until news of the accident broke.

"We all started panicking," he told 7 News. (BBC)