Warning shots fired after two days raise suspicions of pirates . Boats were attacking a US Navy patrol ship . Warning shots land in water and boats turn away , CNN says . Pirates known to be just off African nation of Somalia .
Warning shots fired after two boats raise suspicions of piracy . Boats were approaching a U.S. Navy refueling ship . Warning shots land in water and boats turn away , military says . Pirates known to prowl waters off African nation of Somalia .