Gunmen attacked two ships off the coast of Nigeria's oil-rich southern delta Aug. 4, killing two naval troops protecting the vessels and seizing four foreign workers before fleeing.  Six naval troops were aboard the vessel, which belongs to the Sea Truck oil services company. The Nigerian navy has dispatched boats and a helicopter to the area. Sporadic attacks on oil infrastructure in the Niger Delta have continued despite a 2009 amnesty for militant groups. (AP, Radio Netherlands, Aug. 4)