Three planes narrowly missed colliding with drones near London's Heathrow Airport in the space of three weeks last year, the latest report into air safety has revealed.

In one incident, the pilots of an A320 passenger plane descending into Heathrow noticed a gadget with multiple arms and rotors passing below the plane's right wing at 10,000 feet (3,048 metres).

The separation between drone and plane was just 100 feet (30 metres) vertically and 200 metres (656 feet) horizontally.

The pilot said there was no time to react, a report by the UK Airprox Board, which records air safety incidents, said.

It gave details of three close calls that took place in quick succession in October and November.

While actual collisions are rare, the number of near-misses has increased dramatically in recent years as the popularity of drones has grown.

The incidents underscore increasing concerns about the devices being used near aircraft on approach to Britain’s airports.

There were 70 near-misses between objects identified as drones and aircraft in 2016, compared to 29 in 2015 and six in 2014, the board said.

The A320 incident was one of three near-misses involving planes near Heathrow. In the other two cases, the board said it was either good luck or divine providence that no serious accident had taken place.

Drones must not be flown above 400 feet (120 metres) in Britain. Owners must be able to see them at all times and avoid planes, helicopters, airports and airfields.