Three or four of the damaged items had been on loan, said Christina Haak, deputy director general of the German capital’s state museums.

The cultural sites on Berlin’s Museum Island suffered their most extensive damage to date as a result of the attacks, she told reporters, adding that the sum total of damages could only be given once restoration work was completed.

The vandalism, in which exhibits were targeted with a colourless, oily substance, occurred in three of the UNESCO-protected island’s five museums: the New Museum, the Pergamon Museum and the Old National Gallery.

It remains unclear whether the attacks were carried out by one or several individuals, and how the substance was applied to the works.