A judge in Argentina has ordered the seizure of foreign oil company assets operating in the Falklands Islands.
Lilian Herraez, a federal judge in Tierra del Fuego, ordered the seizure of $156m in bank accounts, boats and other property.
The move comes as Argentina takes a stronger line over the islands, the subject of a dispute with the UK, ahead of elections in October.
Among the assets are those belonging to the UK's Premier Oil Plc and US oil company Noble Energy Inc.
Also listed in the order are Falkland Oil and Gas Ltd, Rockhopper Exploration Plc and Edison International Spa.
Reuters reported that the companies do not generally hold any assets in Argentina or use Argentine waters, but noted a statement from the public prosecutor that said investigators had identified assets, included an office registered to Nobel.
There was no immediate comment from the oil companies.
In graphics: Oil power
The move looks set to become a diplomatic issue on Monday.
The public prosecutors statement said: "The foreign ministry will be notified of the court order so that by diplomatic means and in compliance with international treaties it can be carried out."
Tensions between the UK and Argentina have risen in recent years since the discovery of oil deposits in the disputed islands, a British overseas territory claimed as the Malvinas by Argentina.
Britain and Argentina fought a short war over the territory in 1982, after Argentina's then military dictatorship briefly seized the islands.
(Additional reporting by agencies)