An attacker armed with a rifle, who was fatally shot after ramming his vehicle into one of America’s largest Reform synagogues, was an act of violence, according to the FBI.

Jennifer Runyan, the special agent in charge of the FBI’s Detroit field office, called the incident “deeply disturbing and tragic” and said the FBI is leading the investigation.

“What drove this person into action has to be determined by the investigation,” said Oakland County Sheriff Mike Bouchard.

An unidentified assailant was killed after ramming a pickup truck into a synagogue on the outskirts of Detroit in the US state of Michigan, causing a blaze and triggering a large police response.

Security guards opened fire on the attacker after he smashed through the doors of the Temple Israel synagogue in West Bloomfield, Oakland County Sheriff Michael Bouchard told reporters.

At a news conference on Thursday evening, Bouchard said no synagogue staff or children were injured in the attack, but 30 law enforcement officers were taken to the hospital for smoke inhalation during evacuation efforts.

Single assailant

Law enforcement officials have not publicly confirmed a motive, but the incident comes amid heightened security across the United States following the launch nearly two weeks ago of the US-Israeli war on Iran, which has since expanded across the Middle East.

President Donald Trump described the attack as "terrible" and said it was "absolutely incredible that things like that happen."

Bouchard said the attacker rammed the Temple Israel building with his vehicle before driving down a hallway inside the structure, where he was confronted by security guards.

"We can't say what killed him at this point, but security did engage the suspect with gunfire," the sheriff said.

He said the attacker appeared to be alone in the vehicle and that police dogs were checking the car for explosives.

Michigan Governor Gretchen Whitmer condemned what she described as a "heartbreaking" attack.

White House Press Secretary Karoline Leavitt said President Trump had been briefed on the incident.