Two Marines killed during a `` hostile incident '' in southern Afghanistan . 4,000 U.S. Marines , sailors working to clear Taliban militants from Helmand river valley . U.S. Marines forces launched a similar offensive in the province in August . Forces are trying to gain ground in the region ahead of national elections in late June .
Two U.S. Marines killed during a `` hostile incident '' in southern Afghanistan . 4,000 Marines , sailors working to clear Taliban militants from Helmand river valley . British forces launched a similar offensive in the province in late June . Forces are trying to gain ground in the region ahead of national elections in August .