The Department for the Environment, Food and Rural Affairs (DEFRA) has warned birds infected by the disease could be on their way to the area from France, Germany and the Czech Republic.

A DEFRA spokesman said the birds were believed to be heading for Northamptonshire, East Anglia and the South East.

He said: "Our expert advice is that the areas identified for increased surveillance are those into which birds migrating from the affected parts of Europe are most likely to arrive."

The Government body has asked people working on wildlife reserves in the area to carry out patrols to look for dead birds including ducks, geese and swans.

The Government's chief veterinary officer, Debby Reynolds, said: "The risk of avian influenza to the UK remains low but increased, and our current control and monitoring measures reflect this.

"We will continue to monitor the disease situation and we are keeping our levels of surveillance under review.

"We are also very grateful for the valuable voluntary contribution from the organisations who we work in partnership with to carry out this surveillance work."

Any dead birds which are found in the area will be taken to special laboratories for testing.

Roy Marriott from Northampton-based charity Animals in Need, said his group would be keeping an extra eye out for infected birds.

He said: "We will take extra precautions on top of the ones we already do.

"If we ever come across anything we're not sure about, we always report it to the RSPCA and I would urge people to either contact them or DEFRA if they come across a dead bird."

Earlier this month, three swans were found dead in eastern France.

Their deaths came a month after the virus was found on two poultry farms in the Czech Republic.

Bird flu was found at a Bernard Matthew's farm in Suffolk in February and almost 160,000 turkeys had to be culled.

Anyone who spots a dead bird can call DEFRA's special helpline on 08459 335577.

wayne.bontoft@northantsnews.co.uk