Iran has started six days of naval drills in the Strait of Hormuz, the official IRNA news agency reported, manoeuvres aimed at showcasing its military capabilities in what is a vital oil and gas shipping route.

Naval commander Habibollah Sayyari said the "Velayat 91" drills would last until Wednesday across an area of about 1 million square kilometres in the Strait of Hormuz, the Gulf of Oman and northern parts of the Indian Ocean, IRNA said.

Sayyari said the goal of the manoeuvres were to show "the armed forces' military capabilities" in defending Iran's borders as well as sending a message of peace and friendship to neighbouring countries.

Iranian officials have often said Iran could block the strait - through which 40 per cent of the world's sea-borne oil exports pass - if it came under military attack over its disputed nuclear programme.

Iran held a similar 10-day drill last December and sent a submarine and a destroyer into the Gulf four months ago just as US and allied navies were conducting exercises in the same waters to practice keeping oil shipping lanes open.

Sayyari was quoted as saying on Tuesday that the new drill would test the navy's missile systems, combat ships, submarines and patrol and reconnaissance methods.

A heavy Western naval presence in the Gulf is meant to deter any attempt to block the waterway.-Reuters