Tesla owner Elon Musk has blasted the latest in an escalating wave of attacks on his vehicles as an act of terrorism.

The fire at a dealership in Rome destroyed 17 cars on Monday (local time) and follows global protests at the weekend in response to Musk’s right-wing activism.

Musk offered no proof for his claim, just a single-word comment on a post on X that referred to the fire: “Terrorism”.

It’s not the first time he’s raged about the motives for Tesla vandalism. In March, he labelled a fire that destroyed several vehicles in Las Vegas as “insane and deeply wrong”.

Drone images of the Rome fire showed the burnt-out remains of cars lined up in car park, with two rows of vehicles back-to-back and a third some distance away.

The local fire brigade said the blaze broke out about 4.30am local time. The dealership was partially damaged, but nobody was injured.

The apparent attack on the electric vehicles was being investigated by Italy’s special police unit Digos, a security source said.

Musk, the billionaire tech tycoon who also owns social media platform X, has a prominent role in US President Donald Trump’s administration and is becoming increasingly outspoken in his support of far-right parties in Europe.

On Tuesday (Australian time), he blasted the conviction of far-right French leader Marine Le Pen for fraud as an abuse of the legal system by “the radical left”.

Italy’s Deputy Prime Minister Matteo Salvini, leader of the right-wing League party, took to X to express his support for Musk.

“Too much unjustified hatred against the Tesla car company,” he posted.

“The season of hate and conflict must come to an end as soon as possible. My solidarity goes out to Elon Musk and to all the workers who have been threatened and attacked.”

Also on Monday, two Tesla stores and some cars were vandalised in Sweden’s capital Stockholm and coastal city Malmo, several Swedish media outlets reported.

Public broadcaster SVT reported orange paint was sprayed on a Tesla store in Malmo. It said police had detained four people and were investigating a motive for the crime.

In north-western Germany, police are investigating a fire that destroyed seven Tesla vehicles on Saturday.

Anti-Musk protesters swarm showrooms

The fires in Europe follow wild scenes in the US and abroad at the weekends as crowds protesting at Musk massed outside Tesla dealerships.

They were part of an escalating movement targeting dealerships and vehicles in opposition to Musk’s role as the head of Trump’s new Department of Government Efficiency.

Most of Musk’s estimated $US340 billion ($A539 billion) fortune consists of his stock in the EV company, which he continues to run while also working alongside Trump.

The weekend marked the first attempt to surround all 277 of the car maker’s showrooms and service centres in the US, aimed at deepening the recent decline in Tesla sales.

Pictures posted on social media accounts showed protesters brandishing signs such as “Honk if you hate Elon” and “Fight the billionaire broligarchy.”

There were smaller turnouts in Europe, as well as in Australia and New Zealand, where the anti-Musk sentiment was similar.

In London, about two dozen protesters held signs lambasting Musk outside a Tesla dealership as passing cars and trucks tooted horns in support.

One sign showed a photo of Musk next to an image of Adolf Hitler making the Nazi salute — a gesture that Musk has been accused of reprising shortly after Trump’s January 20 inauguration.

Another protester held a sign with a picture of Musk’s straight-arm gesture that said, “You thought the Nazis were extinct. Don’t buy a Swasticar”.

“We just want to get loud, make noise, make people aware of the problems that we’re facing,” said Cam Whitten, an American at the London protest.

As in Rome, there have been other incidents of Tesla vehicles being set alight and other acts of vandalism that US Attorney General Pam Bondi has decried as domestic terrorism.

Musk indicated at a March 20 company meeting that he was dumbfounded by the attacks, and said the vandals should “stop acting psycho”.

But he didn’t appear concerned about Tesla’s extended sales slump. He told employees Tesla would have sold more than 10 million cars worldwide by next year, up from about seven million cars now.

“There are times when there are rocky moments, where there is stormy weather. But what I am here to tell you is that the future is incredibly bright and exciting,” Musk said.

Musk sells X, mostly to himself

In another development, Musk has sold X – the social media platform formerly known as Twitter – to another of his companies for $US33 billion ($A52 billion).

The deal announced on Friday (US time) consolidates two of Musk’s multiple portfolio companies. Including $US12 billion in debt, the deal is valued at $US45 billion.

“The choice of $US45 billion is not a coincidence,” DA Davidson & Co analyst Gil Luria said.

“It is $US1 billion higher than the take-private transaction for Twitter in 2022.”

The New York Times reported on Friday that X’s value had slumped to $US12 billion in January.

It has struggled to generate revenue since Musk acquired it and turned it into a hotbed of controversial conversation, often fanned by himself. In January, according to The Times, he told employees the company’s revenue was “unimpressive” and it was “barely breaking even”.

Musk announced the transaction in a post on X, saying that the combined entity of the social media platform and his xAI artificial intelligence firm would be valued at $80 billion.

“xAI and X’s futures are intertwined,” wrote Musk. “Today, we officially take the step to combine the data, models, compute, distribution and talent.”

-with AAP