Tighter restrictions are being enforced for poultry keepers across Norfolk, Suffolk and parts of Essex in a bid to halt a worrying rise in bird flu cases.

The UK is in the grip of its worst-ever bird flu outbreak, with more than 150 confirmed cases - including five at farms in Norfolk and Suffolk in the last seven days.

It is a major concern for the region's poultry industry, and also for its wild bird colonies.

As East Anglia's outbreak gathers momentum, the government has declared a regional Avian Influenza Prevention Zone (AIPZ) to prevent the disease spreading further.

It makes it a legal requirement for all bird keepers in the affected area - ranging from commercial farms to backyard hobbyists - to follow a raft of heightened biosecurity measures to protect their flocks.

They include disinfecting clothing, footwear, equipment and vehicles before and after contact with captive birds, cleaning housing continuously, keeping records of mortality and poultry movements, and minimising contact between captive and wild birds.

Keepers with more than 500 birds will also need to restrict access for non-essential people on their sites.

Deputy chief veterinary officer Richard Irvine said the AIPZ was declared after bird flu was confirmed at 10 premises in the affected region since the beginning of September, as well as "several reports" in wild birds.

"All bird keepers in the region must urgently take action now to both prevent disease getting in to flocks and it spreading any further," he said.

"Whether you keep just a few birds or thousands, you are now legally required to introduce stricter biosecurity standards on your farm or small holding.

"It is in your interests to do so in order to protect your birds from this highly infectious and devastating disease."

The localised zone has similar requirements to a countrywide AIPZ which was lifted by Defra in August as the national risk level dropped.

The regionalised AIPZ now in force does not include a requirement to house birds - however "this is being kept under constant review".

Although avian influenza can be devastating for wild birds and poultry flocks, the UK Health Security Agency advise that the risk to public health is very low and the Food Standards Agency says avian influenzas pose a very low food safety risk.

For full details on the requirements and boundaries of the AIPZ, see www.gov.uk/guidance/avian-influenza-bird-flu