For more than two decades, the Medieval treasures of Spain’s Sijena convent have been at the centre of an ownership battle between the autonomous communities of Catalonia and Aragon.

Now, the 44 artifacts kept in Catalonia’s Museum of Lleida have become a flashpoint in the independence crisis, as Aragon takes advantage of direct rule to retrieve the pieces it says were illegally sold off by Sijena's nuns.

On Monday the town of Lleida is braced for a standoff between police ordered in to remove the artifacts and pro-independence Catalans who have vowed to come to their defence.

With the Catalan government dissolved, Spain’s culture minister has stepped into the legal dispute, signing a judicial order for the return of the treasures, with a midnight on Sunday deadline.

Last minute challenges have been launched by local authorities and the museum, arguing that the case is still under appeal and the fragile treasures would suffer if they were then ordered back to Catalonia.

But the Guardia Civil have been authorised to seize them "with force if necessary" - a move which museum director Josep Giralt said risks turning the operation into "a battlefield".