Former Malaysian premier Mahathir Mohamad, 81, suffered a mild heart attack and was taken to hospital on Thursday (November 9), soon after confessing that a feud with his successor was taking a strain on his health. Mahathir was the country's longest-serving premier, having been in power for 22 years before retiring in late 2003. He still wields influence on politics and business and is an adviser to state oil company Petronas and state car-maker Proton. He has been at political war with his hand-chosen successor, Prime Minister Abdullah Ahmad Badawi, for the past six months, accusing him of personal betrayal, mismanagement, nepotism and selling out national interests in dealings with Singapore. Abdullah paid a visit to Mahathir, who is being treated at the National Heart Institute in Kuala Lumpur, but left without speaking to reporters. State news agency Bernama said Mahathir was expected to remain under observation in hospital for one week. Mahathir was taken to Kuala Lumpur's National Heart Institute at about 4 a.m. (2000 GMT) , an official there said. In an interview with Reuters in September, Mahathir said the feud with Abdullah was taking its toll. Mahathir, a former medical doctor, has a history of heart trouble but even in retirement has kept a busy schedule of public engagements and overseas trips. He had heart bypass surgery in 1989. Mahathir's son Mokhzani declined to say if the feud had hurt his father's health but said the former premier had kept a very busy schedule lately, including a visit to New Zealand this week. A controversial figure in the West, outspoken Mahathir is viewed at home as the father of modern Malaysia. He hastened the country's transformation from a mainly rural economy to an industrial trading nation, spending lavishly on infrastructure. Abdullah has struggled to advance his own reforms, such as reining in the budget deficit and shelving major state projects, without incurring the wrath of Mahathir and the ex-premier's supporters who see them as an attack on Mahathir's legacy.