http://af.reuters.com/article/energyOilNews/idAFLDE7180YF20110209 LONDON/ATHENS, Feb 9 (Reuters) - Armed pirates seized a U.S.-bound oil tanker off Oman carrying around $200 million worth of crude on Wednesday in one of the biggest raids in the area to date, escalating the threat to vital shipping lanes. The 333-metre very large crude carrier, the Irene SL, was carrying about 2 million barrels of crude oil, estimated to be nearly 20 percent of daily U.S. crude imports, a day after an Italian tanker was snatched by Somali pirates. "This morning the vessel was attacked by armed men," the tanker's Greece-based manager Enesel said in a statement. "For the moment there is no communication with the vessel."