Senior General Than Shwe, head of Myanmar's ruling junta, left for Singapore to receive treatment for an intestinal tumour, according to media reports.
Than Shwe, 73, who has led Myanmar's junta - the self-styled State Peace and Democracy Council - for the past 18 years, left the country Sunday on a special flight arranged by businessman Tayza, according to the Myanmar-based Mizzima News agency.
An informed source in the government said Than Shwe, ailing for the past year, was suffering from a tumour in his intestines.
His sickness could accelerate a power shift in Myanmar's military hierarchy with many speculating that Than Shwe might be replaced by General Shwe Mann, deemed his chosen successor.
General Maung Aye, the second highest ranking general in Myanmar, is said to lack political support in his bid to lead the junta.
Myanmar has been under military rule since 1962 when former strongman General Ne Win overthrew the elected government of Prime Minister U Nu and launched the country along its disastrous "Burmese Way to Socialism."
Ne Win resigned all political posts in 1988 amid nationwide anti-military protests and passed power to a younger crop of military men who have lorded over the country for the past two decades.