Uganda’s main opposition leader Kizza Besigye has been charged with treason for declaring himself president and challenging the election victory of veteran leader Yoweri Museveni.

Government spokesman Shaban Bantariza said Besigye, who has been under virtual house arrest since a presidential election in February, has been charged with treason because he had declared himself “an alternative president.”

Besigye was handed charges late Friday at a court in the town of Moroto in the northeastern Karamoja region.

His lawyer Erias Lukwago said his client had been denied legal representation, and was to remain in custody until his next scheduled appearance in court on May 25.

The charge, which carries the death penalty, marks an escalation in recent confrontations between the government and Besigye who accuses authorities of beatings and intimidation.

Authorities have blocked social networking sites, citing security concerns around Museveni's official inauguration on Thursday.

Besigye was arrested in the capital, Kampala, on Wednesday, on charges of addressing an illegal assembly and was taken to Moroto town.

Official figures showed that Museveni, 71, secured another term with 60 percent of the vote, extending his three decades in power, while his main rival Besigye garnered 35.4 percent.

Besigye rejected Museveni's victory, saying the poll was a “sham” and called for an independent audit of the results.

Ugandan elections in 2006 and 2011 were marred by violence over the results, sparking widespread protests in the East African country, particularly in the capital.

Museveni, who came to power in 1986 after waging a five-year guerrilla war, is hailed by many Ugandans as providing decades of relative peace and economic stability.

However, experts say the growing economy has not kept up with a rising population. His critics also complain about fraud and a crackdown on dissents.

Besigye was also charged with treason in 2005, but a judge dismissed the case, saying the evidence was insufficient.