Scotland Yard also said it was not prepared to discuss suggestions that those under arrest were of varying Middle Eastern nationalities - nor a claim that another suspect was being sought.

The first two people held were detained after the terror attack on Glasgow Airport on Saturday.

Two men inside a Jeep which tried to ram the terminal building were arrested at the airport.

One, thought to be the driver, suffered severe burns after being engulfed in flames and is in a critical condition in hospital. The other, said to be 27 years old, is in custody.

Later on Saturday night anti-terror officers from the Met and West Midlands Police arrested two people, a 27-year-old woman and a 26-year-old man, on the M6 near Sandbach in Cheshire.

They are being interviewed at a central London police station, thought to be high-security Paddington Green. They are the only suspects so far brought to the capital.

A fifth arrest was made in Liverpool. Scotland Yard said a 26-year-old man was held and two properties in the area searched.

Merseyside Police confirmed that the man was stopped in the Lime Street area of the city centre. The arrest was made on behalf of Metropolitan Police Service counter-terrorism command.