Iran could prevent even "a single drop of oil" passing through the Strait of Hormuz if its security is threatened, and it will increase its military presence in international waters, a naval chief said yesterday, as tensions simmer over Tehran's nuclear programme.

Iran has repeatedly threatened to close the Strait of Hormuz shipping channel, through which 40% of the world's sea-borne oil exports passes, in retaliation for sanctions placed on its crude exports by Western powers. The sanctions were imposed over Iran's nuclear programme, which the West suspects is aimed at creating an atomic weapon.