KAMPALA – Ugandan opposition figure Kizza Besigye was charged with treason on Friday in an escalation of legal troubles stemming from allegations he plotted to remove the country’s long-time leader by force.

Besigye, a four-time presidential candidate in the east African country, sat in a wheelchair as he faced the charges in a courtroom in the capital, Kampala. Treason carries the death penalty in Uganda.

Besigye has been in custody since Nov. 16, when he went missing in the Kenyan capital of Nairobi. Days later, he was presented before a military tribunal in Kampala to face charges over threatening national security.

The Supreme Court stopped his military trial last month, saying court-martial panels cannot try civilians. Besigye’s family, supporters and others wanted him freed immediately, but he was kept in a maximum-security prison and later started a hunger strike.

Besigye has looked frail in recent court appearances, leading to concerns that any harm to him in prison could trigger deadly unrest. Many Ugandans are urging authorities to release him on compassionate grounds.

Amnesty International also called for Besigye’s release, saying his “abduction clearly violated international human rights law and the process of extradition with its requisite fair trial protections.”

This is the second time Besigye has faced treason charges stemming from allegations he tried to overthrow the government. The first case, brought in 2005, failed to take off. This time, he and others are accused of attending meetings, in European cities and elsewhere, during which Besigye allegedly solicited “military, financial and other logistical support to overturn the government of Uganda as by law established,” according to the charge sheet.

Besigye’s attorneys say the charges are politically motivated.

But President Yoweri Museveni has said his political rival must answer for “the very serious offenses he is alleged to have been planning.” Museveni rejected calls by some for forgiveness and instead urged “a quick trial so that facts come out.”

Besigye’s case is being watched closely by Ugandans anxious about political maneuvers ahead of presidential elections next year. Although Museveni is expected to seek re-election, some observers believe he may step aside in favor of his son, Muhoozi Kainerugaba, the top army commander, in a bloodless coup.

Many expect an unpredictable political transition because Museveni has no obvious successor within the ranks of the ruling National Resistance Movement party.

Besigye, a physician who retired from Uganda’s military at the rank of colonel, is a former president of the Forum for Democratic Change party, for many years Uganda’s most prominent opposition group. He is a fierce critic of Museveni, for whom he once served as a military assistant and personal doctor.

Uganda has never witnessed a peaceful transfer of presidential power since independence from colonial rule six decades ago.