Hundreds of supporters of Yoon Suk Yeol, the South Korean president arrested after declaring martial law, stormed a court building early on Sunday after his detention was extended.

They smashed windows and forced entry in an attack the country’s acting leader called “unimaginable”.

Mr Yoon was detained on Wednesday, the first sitting South Korean president to be arrested. He faces allegations of insurrection over his shocking, short-lived declaration of martial law that plunged the country into political turmoil on Dec 3.

Shortly after the court announced its decision at 3am local time on Sunday (6pm on Saturday UK time), Mr Yoon’s supporters swarmed the building, overwhelming riot police who tried to keep them at bay.

They turned fire extinguishers on lines of police guarding the front entrance, then flooded inside, destroying office equipment, fittings and furniture, footage showed.