Britons were urged to stay calm a day after the country announced its first outbreak of the deadly H5N1 strain of avian flu in a wild bird.

Swans are pictured at Richmond Park, in Glasgow in Scotland. Britons were urged to stay calm a day after the country announced its first outbreak of the deadly H5N1 in a swan found dead in a Scottish seaside village. [AFP]

The country's first such influenza case dominated the newspapers, with editorials advocating cautious calm despite fears that the disease will jump to humans causing a deadly pandemic.

Tests were being carried out on 14 more birds after authorities confirmed the lethal virus had been found in a dead swan in Scotland, making Britain the 13th country in the European Union to be hit by H5N1.

The Veterinary Laboratories Agency is carrying out tests for possible bird flu in 12 swans and two other species from Scotland.

Charles Milne, Scotland's chief veterinary officer, said there had been no indication so far that any of these results were positive.

"We will have to wait until the laboratory tests are completed," he added.

Debby Reynolds, Britain's chief veterinary officer, said the discovery of one bird flu case followed tests on thousands of wild birds this year alone, but she refused to speculate whether this was an isolated incident.

"We really don't know," she told the BBC.

The Scottish Executive in Edinburgh said on Thursday a mute swan -- found last week on a harbour slipway in Cellardyke, Fife -- perished from the same H5N1 strain that has killed more than 100 people, mainly in Asia.

A "wild bird risk" area was extended around the spot to 1,000 square miles (1,609 kilometres) as the government hurried to contain the spread of the disease, The Daily Telegraph reported.

All farmers and poultry owners affected by the zone have been asked to keep their animals indoors where possible.

Pets such as dogs and cats living close by should also be kept on a lead.

The authorities have come under fire for taking so long to establish that the dead swan had been carrying the lethal strain of bird flu.

Alex Salmond, leader of the Scottish National Party said on Thursday night: "Now we have a confirmed case in Scotland we need to shorten the time needed for confirmation of test results."

Britain becomes the 13th country in the 25-nation European Union to report a case of a wild bird dying from H5N1, heightening fears of the illness striking poultry farms -- or in a worst-case scenario, mutating into a form that could be highly contagious amongst humans.

Newspapers said confirmation of the disease should come as no surprise because its progress from Asia has been closely documented. They also appealed for a calm, rational response to the development.

"The arrival of H5N1 does not mean we are all going to die," wrote the right-wing Daily Telegraph in an editorial.

It predicted that the most likely victims of bird flu will be poultry farmers, not through sickness but through a drop in chicken sales.

"More dangerous still, however, is the threat of official over-reaction," the newspaper cautioned.

"We should remain calm and not be afraid to eat chicken tonight."

The left-leaning Guardian daily and The Times pushed for sensible, effective measures from the government to ensure the country has the best chance of tackling any serious spread of the disease.

The Guardian also took a global perspective, noting that "no effort should be spared" in preventing a pandemic.

It warned that such an outbreak was far more likely in Asia, where people work in close contact with poultry, than in Europe.

Britain's first case of H5N1 was discovered last October in a parrot imported from South America. But it died while quarantined with birds from Taiwan, enabling the virus to be immediately contained.

In Cellardyke, population 1,900, police manned roadblocks throughout the day Thursday, asking motorists if they had any chickens, ducks or turkeys inside their cars or trucks.

There are 175 registered poultry farms in the wild bird risk area, including 48 which house some 260,000 free range birds -- the ones most vulnerable to infection from wild birds.