Soldiers patrol the Rue Neuve pedestrian shopping street in Brussels on 21 November Getty

Six British men have been arrested by Belgian police after they were seen in three old ambulances just 20 miles from Brussels on 21 November when the capital city was in lockdown. Brussels was on full alert as the government received credible intelligence of a "specific and imminent" Paris-style attack involving firearms and explosives.

Armed anti-terror police moved in on the men close to an Esso petrol station regularly frequented by wanted fugitive, Salah Abdeslam who is still on the run. The convoy of six armoured trucks and a police car encircled the vehicles, which were parked up on the E411 highway in Bierges, south-east of Brussels.

The six Pakistani-born British nationals were being questioned by officers, who found clothes, food and money inside the emergency vehicles, raising the possibility that they may have been travelling to Syria. The ambulances – two Fiats and a Mercedes – had British number plates, according to a Daily Mirror report.

The men, who do not speak French, were said to be cooperating with the authorities. "Shortly before 14:00 hours, we found the ­presence of three old ­ambulances, now transformed into vans, on the highway rest area," a Belgian police commissioner said. "On board were persons of foreign origin, one of who is known to the UK police. These are British citizens of Pakistani origin. They do not speak French but they co-operate."

Brussels' threat level was raised to the maximum level four, and the government urged people to avoid places with large crowds. A series of matches and cultural events were cancelled yesterday (21 November), and the city is still on high alert with soldiers and armed police patrolling the streets.

The metro system remained shut today (22 November), with intelligence services set to review the situation later in the day. Belgian authorities are hunting Abdeslam, 26, who is thought to be a key figure behind the terrorist attacks in Paris on 13 November. The country's media has reported sightings of the wanted Frenchman in or around Brussels.