The UK police have evacuated the homes near an airbase near Fairford, Gloucestershire, over a bombing threat as US military bases in the country are put on high alert.
Police said on Sunday they have arrested several men on suspicion of staging a bombing attack against a military base, reportedly with explosive-laden vans.
Five men were arrested under the Explosives Act on suspicion of preparing a terrorist act, police said.
The five suspects were arrested near Royal Air Force (RAF) Fairford, an airbase used by US forces.
Residents of Whelford, a village next to the airbase, were moved to a nearby leisure center until further notice.
Whelford residents said the police and military forces deployed to the area told them to evacuate immediately. "There's been a major incident," police told them.
"Counter Terrorism Policing can now confirm they are leading an investigation into an incident which took place overnight near RAF Fairford in Gloucestershire," London's Metropolitan Police announced to the public.
Assistant Chief Constable Richard Ocone said police received a call at around 12:45 am "relating to three suspicious vehicles traveling towards RAF Fairford."
"A 400m cordon was put in place around the vehicles, while they were examined by the Army's Explosive Ordnance Disposal Unit," Ocone added.
Deputy Assistant Commissioner Vicki Evans said investigators were in the "early stages of an investigation.
Work is ongoing to establish the full nature of the incident, the police official said.
"We continue to work with Gloucestershire Police to keep the community safe as we work to gather evidence from the scene," she added.
In the meantime, a UK government spokesperson said further details would be made public after investigations ."It would be inappropriate to comment further whilst investigations are ongoing," said
UK Defense Secretary Wes Streeting thanked British armed forces and emergency teams for dealing with the suspected threat.
"We can be reassured that this is being dealt with and it is exactly why our emergency response teams and Armed Forces are on standby 24/7," he said.
Fairford and other US military bases in the UK are on Charlie alert, the second-highest threat level the US Department of War can issue.
"It really does point to the fact that... there was an anticipation that something was up and something was potentially imminent," experts said.
Fairford Air Base shares a long history with the American military.
The airbase was used most recently by US warplanes as a staging point for launching bombing strikes against Iran.