Keepers with 50 or more birds have been ordered to keep their flock indoors. (EPA Images pic)LONDON: The UK government ordered Wednesday all large poultry flocks in England to be kept inside due to "increased risk" from escalating avian influenza cases, as wild birds migrate to Britain.

The mandatory order -- aimed at protecting poultry and other captive birds, and which takes effect Friday -- will apply to keepers with 50 or more poultry birds.

Those who sell or give away eggs or poultry products must also comply.

The move follows officials confirming four bird flu cases in domestic poultry in Britain between Sept 30 and an updated Nov 6 assessment.