GALLE, Sri Lanka/WASHINGTON, March 4 (Reuters) - A U.S. submarine has sunk an Iranian warship off the southern coast of Sri Lanka, resulting in the deaths of dozens of sailors and significantly escalating Washington's campaign against the Iranian navy. Sri Lanka's deputy foreign minister confirmed that the ship was the frigate IRIS Dena, which was returning to Iran after a visit to a port in eastern India.
The incident took place hundreds of


