Uganda is facing a potential political showdown after opposition leader Kizza Besigye returned to the country on the day President Yoweri Museveni is due to be sworn in for a fourth term. Security is tight, especially on the 40km (25 mile) road between the capital, Kampala, and Entebbe airport. Dr Besigye sought medical treatment in Kenya after being injured when he was arrested over anti-government protests. He is a former ally of Mr Museveni, who has been in power since 1986. Dr Besigye left Uganda but returned in 2005 with the introduction of multi-party politics. 'Fraudulent president' Hundreds of supporters have gone to welcome Dr Besigye, who has arrived at Entebbe. Meanwhile, visiting dignitaries, including several African heads of state, arriving in Uganda for Mr Museveni's inauguration are going the other way along the airport road into Kampala. The BBC's Will Ross in Uganda says the government fears the opposition will try to undermine the swearing-in ceremony. There are also concerns that the police could use violence to disperse Dr Besigye's supporters. On Tuesday, they sprayed pink paint to disperse demonstrators in Kampala. On his arrival in Entebbe, Dr Besigye told the BBC that he would not be attending the inauguration of a "fraudulent president". Dr Besigye says he was cheated in February's election, although he mustered only half as many votes as Mr Museveni. The opposition has since been involved in "walk-to-work" protests over the rises in the cost of food and fuel. The government accuses Dr Besigye of trying to organise an Egypt-style uprising. He has been arrested four times. The two used to be close allies, with Dr Besigye serving as Mr Museveni's personal physician when they were fighting President Milton Obote's government in the early 1980s. Dr Besigye had a role in government when Mr Museveni took power but they fell out about 10 years ago. Source: BBC