A Ugandan military general who recently declared he would challenge President Yoweri Museveni in 2021 elections, has been arrested for suspected treason, police said on Friday.A former minister who has often run afoul of Museveni, Lieutenant General Henry Tumukunde on March 3 held a press conference announcing his run for the presidency."My offices and residence under siege. Being put under arrest under presumed treason charges," the 60-year-old wrote on Twitter late Thursday.Ugandan police spokesperson Fred Enanga told AFP that Tumukunde was indeed being held "on charges of treason"."Investigations are ongoing and legal procedures are being followed to have him appear in court as soon as inquiries are complete," he said.The details of the charge were not revealed.Tumukunde fought alongside Museveni in a guerrilla war which overthrew the then-government and installed the incumbent as president in 1986. He was previously arrested and charged with treason in 2005 after he publicly opposed a bid by Museveni to amend the constitution and run for a third term in office.He spent six years in a military jail before moving to house arrest for two years.The charges were dropped in 2013 and by 2015 he was back in Museveni's good books.He waged an often controversial campaign for Museveni's re-election in 2016, dispersing the rallies of opposition candidates and moving around in heavily armed convoys urging the population to vote for the president.On one occasion, he landed a helicopter in the middle of a campaign rally held by an opposition candidate.He was appointed security minister after Museveni won the election, a post which he held until 2018.Museveni, who is seeking a sixth term in office next year, is facing a challenge from singer-turned-politician Bobi Wine, who has also been subject to repeated arrests.