A federal judge in Argentina has ordered the seizure of assets of five companies drilling for oil in the Falkland Islands.

Tierra del Fuego judge Lilian Herraez ordered the authorities to seize boats and other assets worth $156m.

Argentina claims sovereignty of the islands, which it calls the Malvinas.

The oil companies named in the case are not based in Argentina and it is not clear how the measure will be implemented.

Drilling for oil in the territorial waters around the Falklands began in 2010 despite opposition from Buenos Aires.