Eighteen beaches in Thanet, Kent, have been closed after significant oil deposits were discovered along the coastline, with popular tourist beaches in Margate and Ramsgate among those affected.

Thanet District Council reported the incident on Wednesday evening. Officers are inspecting the coast as the authority works to establish where the oil came from. Its source has not been identified.

The council said the decision to close access to the beaches “had not been taken lightly”. A spokesperson urged people to stay away from the affected areas, singling out dog walkers in particular, and asked the public to report any oil deposits on beaches to the authority.

The closures restrict access to some of the district’s popular coastal destinations while inspections continue. The Environment Agency has been approached for comment. The origin of the spill remains the central unresolved question.