Armed and masked men hijacked and set fire to a double-decker bus at dawn on Monday, fuelling fears of a fresh wave of Brexit-related violence in Northern Ireland.

The charred and smouldering remains of the vehicle remained in the Newtownards area on Monday afternoon.

BBC Northern Ireland reported claims from loyalists that they had carried out the attack to mark the passing of the 1 November deadline set by the DUP for walking out of the Stormont executive unless major changes to the Northern Ireland protocol had been secured.

Stormont’s infrastructure minister, Nichola Mallon, said two masked men “muttered something about the protocol” as they held the driver at gunpoint.

“Two masked men entered the bus. They held the driver, a male, at gunpoint, they said something about the protocol, and they then proceeded to spray the inside of the bus with flammable liquid. They forced the bus driver off the bus and then they set it alight,” Mallon told BBC Radio Ulster’s The Nolan Show.

The driver managed to get off the vehicle unharmed but was badly shaken by the incident, the police said. No passengers were on the bus at the time.

The attack, which has echoes of the violence that spilled on to the streets in Belfast and Derry at Easter, was roundly condemned by all parties including the DUP, which said “thuggery and terrorism will do nothing to remove the NI protocol”.

The party’s leader, Jeffrey Donaldson, said political engagement had already secured progress in relation to changes to the protocol and the talks between the EU and the UK must be allowed take their course.

He said when he had set out his timeline for progress, “the EU was saying that fresh negotiations were impossible”.

But in an indication that Donaldson has parked his threat to walk out of Stormont, he said that since then fresh proposals had been put forward by the EU and “serious negotiations have reopened with the UK government”.

“No reasonable person could deny that this represents significant and positive progress. That progress was secured through political action and not violence.”

“Those engaging in thuggery only undermine these efforts and cement the protocol more firmly in place,” he said.

The Ulster Unionist leader, Doug Beattie, described the attack as “utterly disgraceful, depressing and stupid” while the shadow Northern Ireland secretary, Louise Haigh, said it was “utterly reprehensible”.