Switzerland accused Libya on Wednesday of taking “worrying retaliatory measures” against its citizens as relations between the countries deteriorated a week after the Swiss authorities had arres­ted the son of the Libyan leader, Muammer Gaddafi.

The Swiss foreign ministry said two of its nationals had been under arrest in the north African country since Saturday and that Swiss businesses, including the local offices of food group Nestlé and the engineering group ABB, had been ordered to close.