Two more outbreaks of bird flu have been reported in Poland at opposite ends of the country, authorities say, bringing the total number of incidents in Europe's largest poultry producer to five this week.

One of the outbreaks of the H5N8 strain reported on Friday was in the eastern Lubelskie region at a farm about 500 metres from where three cases in turkeys were reported this week.

Until then Poland had not had an outbreak of bird flu since 2017.

In the latest case in the Lubelskie region, 13,000 guinea fowl were affected, regional veterinary officer Pawel Piotrowski said.

An outbreak of the H5N8 strain was also confirmed on a chicken farm in Przygodzice, in the western Wielkopolskie region, Poland's General Veterinary Inspectorate said in a statement.

State-run news agency PAP reported that 65,000 chickens were affected in Wielkopolskie.

"We don't have the results of the tests yet but we already know it is positive," Piotrowski told Reuters by telephone, adding that the guinea fowl would be gassed.

He said over 50,000 birds could be affected in Lubelskie and there was a big risk of the virus spreading in the area as there were a lot of poultry farms close together.

"The area has been secured against people coming in who shouldn't be there ... we are focussing on cleaning the enclosures where birds have been affected," he said.

Local authorities said in a statement on Tuesday that the virus was a subtype of highly pathogenic H5N8 bird flu that can also pose risks to humans.

Piotrowski said that while a danger to humans could not be completely ruled out, the risk of the infection was much lower than for birds for whom it can be deadly.