A top aide to Iran's President Mahmoud Ahmadinejad said on Tuesday that five British sailors detained in southern Gulf waters would be dealt with firmly if found guilty of 'ill intentions.' The five British men on a 60-foot (18-metre) racing yacht were detained last week by the Revolutionary Guards, the elite force said. Ahmadinejad's chief of staff, Esfandiar Rahim Mashaie, said the way to deal with the Britons 'arrested in the Persian Gulf by Iranian forces will be decided by the judiciary,' Fars news agency reported. 'If these people's ill-intention is proven, they will be dealt with seriously and firmly,' he said, adding Tehran had in the past dealt firmly with people who 'entered Iran illegally.' Britain said on Tuesday it has 'no argument' with Tehran over the sailors detained after straying into Iranian waters, stressing that the seizure was a purely consular matter. Seeking to head off a diplomatic row over Iran's seizure of the five on November 25, Foreign Secretary David Miliband stressed that they were being treated well. 'There is certainly no confrontation or argument,' he told BBC radio, a day after London went public about the seizure. 'This is a purely consular matter, and we look forward to it being treated as such. 'As far as we are aware these people are being well-treated, which is right and what we'd expect from a country like Iran,' he added. The seizure, which recalls the detention of 15 British navy personnel in 2007, comes amid already heightened tensions between Tehran and the West over Iran's nuclear plans. The five Britons were sailing from Bahrain to the start of a race in the emirate of Dubai when their yacht, 'The Kingdom of Bahrain,' was stopped last Wednesday in the Gulf, the Foreign Office said. The yacht is believed to have been intercepted near the Iranian-controlled island of Abu Musa, whose ownership is disputed by Iran and the United Arab Emirates, a Bahraini interior ministry source told selfnews. Miliband stressed the latest incident was different from the one in 2007, which involved military personnel. 'It is important to say that these are civilians, not Royal Naval personnel,' he said. 'They are yachtsmen, they were going about their sport and it seems they may have strayed inadvertently into Iranian waters.' The Revolutionary Guards navy chief, Ali Reza Tangsiri, said the Britons had been arrested by his forces. 'The British intruders have been arrested by the Guards' navy,' he told Fars, adding that 'the movements in the Persian Gulf are under the supervision of Sepah (Guards).' The yacht may have been drifted into Iranian waters after breaking its propeller en route to the Dubai-Muscat Offshore Sailing Race, which started last Thursday, British media reports said. The crew have been named as Oliver Smith, Oliver Young, Sam Usher, Luke Porter and David Bloomer, according to informed sources in London. On a visit to Seoul, Iran's Nobel peace laureate Shirin Ebadi called for their release. 'I believe the Iranian government has arrested them without warnings. They must be released as soon as possible,' she told reporters. Ebadi, a lawyer, said the Britons might have entered Iranian waters by mistake. 'In this case, (Iranian) maritime police should have escorted them out into international waters,' she said through an interpreter. Charles Porter said he had spoken to his 21-year-old son Luke on a mobile phone since the incident and he appeared to be in good spirits. 'From what we understand there was an oil field on their charts -- which is a restricted area -- so they chose to go one side of it,' Porter said, adding the yacht may therefore have strayed too close to an Iranian island. The Foreign Office said it could not say where the Britons were being held or if they were in prison. In the 2007 incident, eight sailors and seven marines were captured on March 23. Britain insisted they were in Iraqi territorial waters, while Tehran said they were in Iranian waters. During the 13 days they were held, the 14 men and one woman were not mistreated but were paraded on Iranian television, sparking anger from Britain and other Western governments. 