Argentina will take legal action against oil companies operating around the disputed Falkland islands, Foreign Minister Hector Timerman said Thursday. "We will take the required legal, administrative, civil and criminal actions against oil companies currently involved in drilling," he told a press conference, amid months of rising tensions over the South Atlantic islands claimed by Argentina since 1833, but held by Britain. He noted that in the past Buenos Aires had already "notified these firms that they were acting illegally." "We will also send warnings to companies which might be interested in these activities, serving them notice of the possible administrative, civil and criminal sanctions they might face," he added. Tensions have flared anew since 2010 when Britain authorized oil companies to explore for oil in Falklands waters, and have sharpened with the deployment of a British warship to the islands. On Wednesday the Argentine Senate unanimously passed a measure known as the "Ushuaia declaration" that asserts sovereignty over the Falklands. The draft document drawn up February 25 in the southern city of Ushuaia reaffirms "the legitimate" sovereignty of Argentina "over the Malvinas," as the islands are called in Spanish, "South Georgia, South Sandwich and the surrounding maritime areas." The text was adopted ahead of the 30th anniversary of the war fought between Argentina and Britain over the remote island chain, and denounces "the persistent colonialist and militarist attitude of the United Kingdom." Argentine troops seized the islands on April 2, 1982, only to be routed by British forces 74 days later. In all, 649 Argentine troops, 255 British troops and three Falkland Islanders were killed in the brief but bloody conflict.