Iran has launched a large-scale air defense exercise which it said was aimed at sending a "strong warning" to those threatening it with military strikes.
Some 8,000 troops are participating in the four-day drill, which began on November 12.
The exercise is said to cover an area stretching 850,000 square kilometers in Iran's eastern regions.
It appears unconnected to an incident last week when two Iranian fighter jets fired on a remotely-operated U.S. drone.
The start of the exercise, announced on the website of the Islamic Revolutionary Guards Corps, was originally scheduled for early October but postponed without an official explanation.
The United States and Israel have not ruled out military action against Iran if Tehran continues nuclear research the West fears is aimed at developing nuclear weapons.
Based on reporting by Reuters and AP