Ugandan police have raided the offices of at least two newspapers following reports that President Yoweri Museveni is grooming his son to succeed him. Two radio stations have also been taken off air, the state-owned New Vision newspaper reports. Last week, newspapers reported claims allegedly made by an army general that those opposed to Mr Museveni's son succeeding him risk being killed. Mr Museveni, in power since 1986, is due to step down in 2016. There has been long-standing speculation that his son Muhoozi Kainerugaba, a brigadier in the army, is being groomed to succeed him. The government has denied having any such plans. 'Anarchic' Uganda's leading private newspaper, the Daily Monitor, and another newspaper, Red Pepper, last week published a confidential letter, purportedly written by army General David Sejusa, calling for an investigation into allegations of a plot "to assassinate people who disagree with this so-called family project of holding onto power in perpetuity". The police raid was authorised by a court and was aimed at retrieving the alleged letter from the offices of the two newspapers, New Vision reports. Two radio stations linked to Daily Monitor, Dembe FM and KFM, had also been "switched off", it reports. Daily Monitor Managing Director Alex Assimwe told BBC Focus on Africa that about 50 armed policemen had raided its newsroom. "They must be under instructions. It is horrifying that in this day and age you should employ all these methods - shut down a media house to get to a document," he said. He added that the newspaper did not have the document, and was not compelled to divulge its sources to the police. "The law protects us," he said. Analysts say Gen Sejusa's letter suggests a power struggle within the military top brass, as the older generation of army officers gradually loses power to the new guard, of which Brig Kainerugaba is a prominent member, AP news agency reports. Gen Sejusa fought alongside Mr Museveni when his rebel movement seized power in Uganda in 1986. Top army commander Gen Aronda Nyakairima said Gen Sejusa was being investigated, AP reports. His letter "champions the agenda of the radical and anarchic political opposition, hence rendering him partisan", Gen Nyakairima said, it adds. Gen Sejusa's lawyer Joseph Luzige said his client was out of the country, and would not return at the moment as he risked being arrested, AP reports. He would stay out of Uganda until his legal team prepares for any potential cases against him, Mr Luzige added, it reports.