Clusters of unidentified drones spotted in New York and New Jersey

FBI investigation under way as residents across US north-east report mysterious aircraft sightings for weeks

A spate of mysterious drone sightings have been reported in New York and Philadelphia as the FBI continues investigating similar sightings across New Jersey over the past month.

Since mid-November, local residents in several counties in New Jersey have reported seeing clusters of drones - and in recent days, additional drone sightings have been reported in parts of Pennsylvania and New York's Staten Island.