(Adds new statement from Nuremberg, details)

By Louis Charbonneau

BERLIN, June 24 (Reuters) - The deadly strain of the bird flu virus has resurfaced in Germany in the bodies of at least three dead birds found in the state of Bavaria, Germany's first confirmed cases this year, officials said on Sunday.

The corpses of several more birds found in the southern state are being analysed to see if they also contain the deadliest strain of the H5N1 virus, a spokeswoman for the Bavarian city of Nuremberg said.

The country's top veterinary laboratory, the Friedrich Loeffler Institute, confirmed that three wild birds -- two swans and a goose -- found in two lakes near Nuremberg had tested positive for the worst strain of the H5N1 virus.

"Over the next few days the city of Nuremberg will be supported by a federal epidemiological team which will scientifically investigate the causes and background of the infection cases," the city of Nuremberg said in a statement.

It said that poultry farmers in the region were required to confine all poultry birds to closed stalls. It added that as of Saturday a 21-day ban had been imposed on bringing poultry birds or products in or out of the area, now a quarantine zone.

City officials also warned cat and dog owners not to allow their pets to roam freely in the quarantine zone.

Germany quickly passed this information on to the European Commission.

"Highly pathogenic avian influenza H5N1 was detected in more than 700 wild birds in the EU in 2006," the Commission said in a statement. It added that the infected swans in Bavaria were the European Union's first cases reported in wild birds in 2007.

DEAD BIRDS

Five other dead birds found near Nuremberg tested positive for the H5N1 virus but it remains unclear whether they have the deadly Asian strain, German officials said.

In addition to the dead swans and goose, the body of at least one wild duck has been confirmed to have some form of the H5N1 virus, Nuremberg city said.

The Friedrich Loeffler Institute is carrying out tests on the animals to determine which H5N1 strain they carried.

Last year, some 13 European Union member states had confirmed cases of bird flu -- Germany, Austria, Denmark, Italy, Greece, Britain, the Czech Republic, Poland, Slovakia, Slovenia, Sweden, France and Hungary.

Czech veterinarians started culling several thousand turkeys on a farm last week after tests confirmed the country's first outbreak of a deadly form of bird flu in poultry.

Bird flu has been spreading across southeast Asia, killing two people in Vietnam this month, the first deaths there since 2005.

Globally, the H5N1 virus has killed nearly 200 people out of over 300 known cases, according to the World Health Organisation. None of the victims were from Europe.

Hundreds of millions of birds have died or been slaughtered. (Additional reporting by Holger Hansen in Berlin and Jeff Mason in Brussels)

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