The Twitter posts threaten to increase tension between the two countries at a time when British companies are beginning to explore for oil and gas in the region. Last week, in what is thought to have been the first incident of its kind in four years, an Argentine military ship confronted a trawler from the Falklands and accused it of fishing illegally. The Argentine crew contacted the fishermen, who were several miles inside Falklands waters, and demanded their details. The boat, from Port Stanley, eventually moved away.