LONDON/DUBAI — Iranian oil tankers are sending incorrect satellite signals that confuse global tracking systems and appear to conceal voyages made by other ships to Syria, which, like Iran, is subject to international sanctions. The two countries are close allies and have helped each other deal with shortages by swapping badly needed fuels such as gasoline for diesel. Sanctions imposed on Iran to hamper its nuclear program have blocked sales of its oil to the West and made it increasingly difficult for Iran's fleet to obtain insurance and financing for deals with Asian buyers in China, India and South Korea. Western sanctions have also isolated Syria, preventing it from exporting oil, while blocking fuel and weapons imports. Iranian state tanker company NITC has already changed many tanker names as part of its response to sanctions, though shipping experts say such a tactic would not confuse anyone in the business about a vessel's whereabouts. Now tanker tracking data monitored by Reuters and shipping specialists have highlighted a more subtle twist. Large vessels must transmit their identity and location to other ships and coastal authorities using an automatic satellite communication system, but in the last month Iranian vessels sailing in Asian seas have sent signals that took over the identity of other vessels, so the same ship appeared to be in two places at once. “It is of course possible to manipulate or falsify information in these messages,” said Richard Hurley, a senior analyst at IHS Fairplay, a maritime intelligence publisher. At least three Iranian oil tankers are transmitting such false signals, effectively taking over the identity of Syrian-owned vessels travelling between Syria, Libya and Turkey. All the vessels in question were registered in Tanzania. “In the past months we witness a recurring pattern of vessels sailing the Tanzanian flag that transmit the same MMSI number (a satellite signal that provides information on a ship's identity and position),” said Windward, a firm that provides maritime analytics technology. — Reuters