Police in Poland have detained at least 11 people after a naked demonstration at the Auschwitz museum, on the site of the former Nazi death camp.

The museum said “a group of people killed a sheep, undressed and chained themselves together”.

The incident took place beneath the main gate, which bears the infamous slogan “Arbeit Macht Frei” [“Work Makes You Free”].

The motive behind the demonstration was unclear, officials said.

A firecracker was also launched in the car park.

Museum guards immediately intervened and ordered the group to dress. Police attended the site in the southern city of Oswiecim, which was closed to visitors.

The individuals involved are said to be aged 20 to 27, and their identities, nationalities and motive are unknown.

They are thought to be mainly Poles, but Poland’s state news agency PAP reported that Germans and Belarusians were among the detainees.

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The demonstrators could be charged with insulting a monument or symbolic place, which may result in a fine or a restriction of liberty, police said.

Local media reported that they used a drone to film the disturbance, and draped a white banner with the red text “love” over the gate.

Some Polish media say the action was a protest against the war in Ukraine, BBC Warsaw correspondent Adam Easton reports.

In its statement the Auschwitz museum said: “Using the symbol of Auschwitz for any kind of manifestations or happenings is outrageous and unacceptable. It is disrespectful to the memory of all the victims of the German Nazi Auschwitz concentration and extermination camp”.

According to the museum, 1.1 million people, including 1 million Jews, were murdered by the Nazis at the camp.