TEHERAN, Iran - A US aircraft carrier entered a zone near the Strait of Hormuz that is now being used by the Iranian navy for military drills, an Iranian official said on Thursday amid rising tensions over the key oil-transit channel.

"A US aircraft carrier was spotted inside the manoeuvre zone ... by a navy reconnaissance aircraft," Commodore Mahmoud Mousavi, the spokesman for the Iranian exercises, told the official IRNA news agency.

Iranian aircraft recorded video and photos of the US vessel, he added.

Mousavi also said the Iranian navy's aircraft and helicopters continued surveillance and reconnaissance operations during the sixth day of major naval drills to monitor activities of all units in the area of the military exercises.

The US aircraft carrier was believed to be the USS John C. Stennis.

US officials announced on Wednesday that the ship and its accompanying battle group moved through the Strait of Hormuz, a narrow stretch at the entrance to the Gulf that is the world's most important choke point for oil shipments.

War of words

Iran's navy chief Admiral Habibollah Sayyari said on Wednesday that closing the Strait of Hormuz, the passage at the mouth of the Gulf through which about 15 million barrels of oil pass daily, would be "easier than drinking a glass of water".

On Tuesday, Mohammad-Reza Rahimi, Iran's vice-president, said his country will close the Strait of Hormuz, if Western nations impose sanctions on its oil shipments.

The comment drew a quick response. The US Defense Department warned on Wednesday that such action "will not be tolerated".

Separately, Bahrain-based US Navy 5th Fleet spokeswoman Lieutenant Rebecca Rebarich said the navy is "always ready to counter malevolent actions to ensure freedom of navigation".

Iran has repeatedly said it could target the Strait of Hormuz if attacked or its economy is strangled.

China hopes stability can be maintained in the Strait of Hormuz, Foreign Ministry spokesman Hong Lei said on Thursday during a news conference.

Ye Hailin, a researcher with the Institute of Asia-Pacific Studies of the Chinese Academy of Social Sciences, dismissed the prospect of imminent military conflict triggered by the Iranian exercise, saying the regional situation is not ready for such conflicts.

If the US attacks Iran, it would further complicate the regional situation, which is not what the US wants, he said.

"As for Iran, despite all the publicity and gestures, it is not the country's style to resort to military force, and Iran does not need to use military force directly to challenge the US," he added.

Ye said Iran does not need to block the shipping, the threat itself is a political gesture that can cause a havoc on the oil market, which would be effective enough. Some US analysts have doubted Iran's ability to block the strait, saying the country's navy is not large enough for a sustained physical blockade of the Strait, but it does have mine-laying and missile capabilities, according to Reuters.

Ye also said Iran can afford the economic consequences of blocking of the strait because it has already suffered sanctions for years.

But a possible war triggered by a blockade is a much bigger concern, which would prevent the country from turning to the last resort, he added.

China Daily-AFP-AP-Reuters-Xinhua