London airports tighten security

The national threat level has been raised to critical

Increased armed patrols have been deployed at two London airports following a suspected terrorist attack at Glasgow Airport.

Armed police are patrolling Heathrow and London City airports in light of the current terror threat.

Passengers have also been warned of delays after restrictions were placed on cars entering forecourts.

Airport operator BAA said forecourts were closed to traffic on orders from the police.

It follows an incident in Scotland on Saturday in which two men drove a burning car into the terminal building at Glasgow Airport.

Nationwide ban

The suspected terrorist attack has prompted a ban on the picking up and dropping off of passengers by vehicles at airport forecourts nationwide.

BAA corporate affairs director Duncan Bomfield said: "Forecourts at airports are basically shut or very restricted to vehicles, with cabs being directed to short-stay car parks."

"There's no dropping off at the moment and there certainly won't be for a while. Fortunately, at Heathrow Airport, most passengers are heeding our advice and arriving and leaving by public transport."

The move has caused long queues of traffic on the M2 near Gatwick Airport.

The UK threat level has been raised to critical - meaning that a terrorist attack is expected imminently.