Residents reporting swarms of mysterious black flies in parts of Colchester have been told: "Don't be afraid".

The black insects known as St Mark's flies have prompted residents to contact the council environmental health team.

Colin Daines, Colchester council environmental control manager, reassured people that the flies - small and black with a thin body - posed no threat. They bear no likeness to house flies.

He said: "People should not be too concerned; they are completely harmless. They feed on roots and vegetation, but do swarm in large numbers. I have been told they are very gregarious - I suppose you could call them party flies," he added.

Mr Daines said if anyone was concerned they could contact the environmental health department for advice.

"At this time of year they tend to swarm and that's what people are seeing," he said.

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