Iran says it will take serious measures against five British yachtsmen being held in the Gulf if it proves they had “evil intentions.”A close aide to President Ahmadinejad issued the warning, almost a week after the crew was detained by Iranian naval forces. A Bahrain-based journalist is among the five, as is Oliver Young, 21, whose father says it appears the captives are being well treated. “We spoke to him briefly,” David Young said. “The reporter on board has got a local mobile phone and they were actually allowed to make a quick call yesterday so we had a quick chat to him. They are all being looked after. They are all being fed well. They are ashore somewhere on the island that apparently was where they were arrested nearby but they seem in good spirits.” British Foreign Minister David Miliband says the crew, sailing from Bahrain to Dubai for a race, may have inadvertently strayed into Iranian waters. The UK is playing down parallels with an incident in March, 2007, when Iran seized eight British Royal Navy sailors and seven marines off its coast. They were freed unharmed the following month.