Iranian forces fired what military officers said was a new generation of surface-to-air missiles Monday during a wide-ranging naval exercise that focused on striking hypothetical unmanned aircraft and vessels in international waters to the south of the country, Iranian media reported.

The missiles were fired on the fourth day of a six-day naval exercise that started Friday, when Iran announced that it had begun the exercises that would test a new version of its Thunder surface-to-air midrange missile. They were meant to demonstrate the country's defense of its territorial waters, the official Islamic Republic News Agency said.

In addition, Iran deployed warships and helicopters to escort commercial ships and oil tankers as part of a drill meant to show the country's ability to combat piracy, it reported. The exercise also included drills using Iranian-made drones and submarines.

The semiofficial Fars news agency quoted an Iranian naval commander, Rear Adm. Alireza Nayyeri, as saying that the navy had "boosted and upgraded" the capability of its domestically manufactured drone aircraft.

The exercise was conducted in the Strait of Hormuz, a strategic waterway through which much of the world's oil and cargo shipments pass, as well as in the Gulf of Oman, the Gulf of Aden and the northern Indian Ocean, IRNA reported. Accounts in the state-run media said the war games covered a 400,000-square-mile area.

Iran holds military exercises regularly to demonstrate its capabilities in the strategic Persian Gulf region, where about 30 percent of the world's energy supplies are transported.

NEW YORK TIMES