TEHRAN, Iran (AP) — Iran's navy warned a U.S. warship to leave an area where Iran has been conducting a naval drill near the narrow Strait of Hormuz at the mouth of the Persian Gulf, the semi-official Fars news agency reported Wednesday. The U.S. Navy denied that its operations in the region were affected.

The Iranian navy chief, Adm. Habibollah Sayyari, was quoted as saying that the U.S. warship received two warnings before leaving the region.

"They were warned once by maritime patrol aircraft and once again by the Alborz destroyer," he said. "The U.S. warship left the region immediately after receiving the warning," he added, saying he believed that the Americans had approached the area to "learn our tactics."

Iran said the naval drill got underway Wednesday over an area of 3 million square kilometers, including part of the Strait of Hormuz, through which one fifth of the world oil supply passes, as well as the Gulf of Oman and neighboring parts of the Indian Ocean. It is the first Iranian naval exercise since 10 U.S. sailors were briefly captured by Iran earlier this month after drifting into Iranian territorial waters.

Cmdr. Kevin Stephens, a spokesman for the U.S. Navy's 5th Fleet, offered a different version of events.

Stephens said the U.S. is aware of the Iranian exercise and that it has not altered U.S. naval operations in any way. Iran had announced plans to close off certain areas for the drill, but he said this is "common practice for any navy conducting such training at sea," he said.

"Our forces similarly announce closure areas for our training events. We do not consider such announcements to be 'orders,'" Stephens said.

Iran conducts similar exercises annually and the U.S. does not see this year's as a change in Iranian behavior, Stephens added.

He said the exercise may increase the chances of U.S. forces interacting with Iranian warships, but added that U.S. Navy vessels are routinely approached by Iranian warships as they operate in the region. Most of those encounters are conducted "in a safe and professional manner, recent events notwithstanding," he said.

The 5th Fleet is the U.S. Navy's regional counterweight to Iran and is based across the Gulf from Iran in the island kingdom of Bahrain.

On Tuesday, Sayyari said many types of missiles and torpedoes will be launched during the maneuvers.

Iran occasionally holds military maneuvers to ensure the preparedness of its forces and to demonstrate its military capabilities in the region. The county has more than 2,000 kilometers of shoreline facing the Persian Gulf and the Sea of Oman.

Associated Press writer Adam Schreck in Dubai, United Arab Emirates, contributed to this report.