U.S. and Afghan forces backed by a giant B-52 bomber, A-10 attack aircraft and helicopters killed an estimated 16 militants in southern Afghanistan in the past two days, the U.S. military said on Thursday in a report carried by Reuters. The militants were killed on Tuesday and Wednesday during an operation codenamed Vigilant Sentinel aimed at ensuring security for Sept. 18 parliamentary and provincial council elections. The U.S. military said six militants were were killed on Tuesday after Afghan and U.S.forces saw them planting improvised explosive devices in Shinkay district of Zabul province. An Afghan and U.S. patrol also pinned down another group of militants southeast of the town of Tarin Kot and called in a B-52 bomber, A-10 attack aircraft and attack helicopters, it said, adding that casualties there were being assessed. In other incidents on Wednesday, five militants were killed by aircraft and ground fire northeast of Tarin Kot five more in Kandahar province, the statement said, adding that there were no U.S. casualties or damage in any of the incidents. --More 1108 Local Time 0808 GMT