Seven people, including six men and one woman, were arrested as part of a "large pre-planned" counter-terrorism raid by police in the British city of Birmingham, local police announced on Monday.

A statement released by West Midlands Police said the six men, all aged between 25 and 32, were suspected of commission, preparation or instigation of an act of terrorism in the UK.

They arrested at or in the vicinity of their home addresses by unarmed officers between approximately 11:30 Sunday night and one o'clock Monday morning.

The woman suspect, 22, was arrested for alleged failing to disclose information about the suspected plot.

"The operation is in its early stages so we are unable to go into detail at this time about the nature of the suspected offences," said Assistant chief constable Marcus Beale.

"However, I believe it was necessary to take action at this time in order to ensure public safety," the police officer added.

The suspects are currently being held for questioning at a police station in the West Midlands Police area, while searches at some properties are being conducted by specialist teams, the police statement said.

The terrorism threat level in England, Wales and Scotland remained unchanged at "substantial" on Monday, meaning that a terrorist attack is a "strong possibility."

VietNamNet/Xinhuanet