No one was injured in the attack early on Monday, which shattered windows in nearby homes and left the vehicles charred shells.
Religious and political leaders condemned what Prime Minister Keir Starmer called a "horrific" anti-Semitic attack.
"Anti-Semitism has no place in our society and it's really important that we all stand together at a moment like this," he said.
Officers were called to Golders Green, a north London neighbourhood with a large Jewish population, after receiving reports of a fire, the Metropolitan Police force said.
Four ambulances belonging to Hatzola Northwest, a volunteer organisation that provides emergency medical response, were damaged.
Multiple gas cylinders on the vehicles exploded, breaking windows in an adjacent apartment block.
What appeared to be footage from a security camera showed three figures in black wearing hoods carrying a canister toward one of the ambulance before flames erupted around the vehicle.
Police said they were looking for three suspects.
The attack spread fear and alarm through Britain's Jewish community, which feels increasingly vulnerable.
Shomrim, a non-profit organisation that operates a neighbourhood watch in the area, condemned the attack on the social network X as "a targeted and deeply concerning incident affecting a vital emergency service serving the local Jewish community".
The number of anti-Semitic incidents reported across the UK has soared since Hamas's October 7, 2023, attack on Israel and Israel's ensuing war against Hamas in Gaza, according to the Community Security Trust, which works to protect the Jewish community.
The group recorded 3700 incidents in 2025, up from 1662 in 2022.
In October 2025, an attacker drove his car into people gathered outside a Manchester synagogue to celebrate the Jewish holiday of Yom Kippur and stabbed one person to death.
Another person died during the attack after being inadvertently shot by police.
Some members of the community criticise Starmer's Labour Party government for failing to prevent pro-Palestinian demonstrations tipping into anti-Jewish speech and acts.
Peter Zinkin, a Conservative politician who represents Golders Green on the local council, said the community felt "distress and anger".
"Burning ambulances in the middle of the night is a disgrace," he said.
"And you have to ask yourself, why did it happen? And the reason I'm afraid that it happened is that the government and the media, particularly certain parts of the media, have validated anti-Semitism on a countrywide scale."
Archbishop of Canterbury Sarah Mullally, the head of the Anglican Church, said "such acts of violence, hatred and intimidation have no place in our society".
Chief Rabbi Ephraim Mirvis called it a "sickening assault".
"At a time when Jewish communities around the world are facing a growing pattern of these violent attacks, we will meet this moment with shared resolve and stand together against hatred and intimidation," he wrote on X.
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