Armed police have arrested a man wearing a clown mask and brandishing a fake gun as the "killer clown" craze continues.

Exasperated police forces across the UK have warned that pranksters or criminals using the costumes to scare innocent members of the public will face arrest, as they deal with a wave of reports.

In one of the latest incidents, officers from Scotland Yard's aviation unit held a suspect in Hillingdon, west London, on Tuesday, about five miles (8km) from Heathrow Airport, after he was spotted wearing the mask and carrying a fake firearm.

A force spokesman said: "On Tuesday October 11 police were called shortly before 3.45pm to reports of a man seen in a car with a suspected firearm wearing a mask in the Church Green area of Hayes.

"Armed officers from Heathrow's Aviation Policing unit stopped the car on Uxbridge Road, Hillingdon, and an imitation firearm was recovered.

"The driver was arrested on suspicion of possession of an imitation firearm and taken into custody at a west London police station."

The "killer clown" craze, where people dressed as murderous-looking clowns try to scare members of the public, started in the United States before spreading across the pond.

In 2013 in Norfolk and in 2015 in Kent there was a flurry of similar reports of pranksters wearing the costumes in an attempt to frighten schoolchildren or other members of the public.

The Hillingdon arrest took place just over a mile (1.6km) from Brunel University, where sightings of a clown clutching a chainsaw on Saturday were reported to police. A 19-year-old man was arrested and released on bail until later this month.

A teenager who gave his name only as Kenny told the Evening Standard that he was being filmed for his YouTube channel that evening and was only chasing his friends.

In another creepy encounter, two schoolgirls in Hither Green, south-east London, were chased by a man wearing a clown mask and reportedly brandishing a knife on Monday.

On Tuesday, an 18-year-old, from Penyrheol, Caerphilly, was landed with what is thought to be the first criminal record connected with the "killer clowns" when he was issued with a fixed penalty notice and fined GBP90 for a public order offence.

Gwent Police said they responded to reports that a man dressed as a clown had been intimidating children outside St Cenydd Comprehensive School in Caerphilly.

In Kent, police revealed they received reports of 59 clown-related incidents between October 7 and 10, and on Sunday Thames Valley Police said they had 14 such reports in the space of 24 hours.