Libya is facing its most critical moment since the ousting of Muammar Gaddafi with armed groups blockading oil fields and terminals, choking output to a 10th of normal levels and threatening economic disaster. With the government forced to import fuel to keep power stations running and queues growing at petrol stations, the prime minister, Ali Zaidan, has repeatedly threatened to send troops to retake striking ports. But the leader of rebels blockading ports in Cyrenaica, home to the bulk of Libya's oil, said such a move would be tantamount to a "declaration of war". Ibrahim Ali Jathran, commander of troops...