Militiamen trying to wrest control of the oil-rich Niger Delta threatened on Tuesday to launch a “full-scale armed struggle” on petroleum-pumping operations in Africa’s largest crude oil producing nation, urging foreign oil workers to leave the region. A military spokesman, however, called the threats “empty.” Major oil companies played the warnings down, saying they won’t seriously affect exports and issuing no orders to staff to pull out. The threats, nevertheless, helped push world oil prices to historic highs of $50 per barrel Tuesday. Full Story