The discovery comes as the European Union agreed to new measures to counter the flu threat, including a three-kilometre protection zone and 10-kilometre surveillance zone be installed around outbreaks of flu in wild birds.
In the feared case of the disease transferring to poultry, members of an EU committee on animal health approved buffer zones be set up, which could cover an entire region or country, and in which the transport of poultry would be restricted.
EU health commissioner Markos Kyprianou reiterated that there is no need for the public to panic.
"While we have to learn to live with periodic outbreaks of avian influenza in wild birds, the European Union is making every effort to contain avian influenza in wild birds and seek to prevent it reaching commercial poultry," he said.
"It is understandable that the public is concerned, but they need not be unduly alarmed as all the necessary measures are being, and will continue to be taken," he added.
German birds infected
In Germany, Ms Merkel appeared on the national television channel ZDF to call on Germans to be "cautious and take care".
First results from tests on 40 dead birds carried out by an animal health institute showed that 10 of the birds were carrying the highly pathogenic form of H5N1, the health ministry of the Mecklenburg-Pomerania region said.
Final test results are expected in three days from an EU-approved laboratory in Weybridge, Britain.
The new cases were detected in nine swans and one goose which had been found near to where two other dead swans and a hawk with the virus were found on Wednesday.
In one of the new cases, the dead swan was ringed and had come from Latvia, and likely died in late January, the ministry said.
German authorities have ordered all poultry to be kept enclosed so domestic hens, ducks and geese do not come into contact with infected wild birds.
The confinement order is due to be in force until the end of April.
The German Agriculture Minister Horst Seehofer is due to visit Ruegen on Saturday.
Meanwhile, a dead swan found in northeast Slovenia has tested positive for bird flu, in the country's first confirmed case of the virulent form of the virus.
It was found last week near Maribor, close to the Austrian border.
Austria has confirmed its third case of bird flu in a wild swan found dead near the southern city of Graz.
Greece has announced that two more wild swans tested positive, bringing to six the total number of cases in the country.
Africa on alert
Nigeria has accelerated its drive to stop the continent's first bird flu outbreak from spreading to humans, as neighbouring Niger announced a state of alert and an emergency plan worth around A$5 million to monitor the border with Nigeria, where the virus has been detected.
Nigerian President Olesegun Obasanjo announced a campaign to eradicate bird flu, saying people at risk will be vaccinated and birds within a five-kilometre radius of infected poultry farms will be culled.
There have been reports of another potential outbreak in an additional state.
Already, eight Nigerian states have reported bird flu outbreaks.