Myanmar's President Thein Sein was resting at his home in Yangon on Friday after military doctors paid a house call but an adviser said his condition was "nothing to worry about."

It was not immediately clear what was ailing the 67-year-old leader, but he could be suffering from exhaustion due to a heavy workload, presidential adviser Ko Ko Hlaing told The Associated Press.

"The president's health condition is not critical and there is nothing to worry about," he said, declining to elaborate. The health of a leader is a sensitive topic in Myanmar and is typically not officially discussed.

Thein Sein has a heart condition and reportedly traveled to Singapore earlier this year for a new pacemaker.

Since taking office in March 2011, Thein Sein has won international praise for overseeing Myanmar's transition from military rule to fledgling democracy. He has spearheaded a wave of reforms that have surprised even his staunchest critics.

Meanwhile, the government has not yet addressed the several-week absence of Vice President Tin Aung Myint Oo, one of two vice presidents.

Government officials and family members say that Tin Aung Myint Oo resigned in early May for health reasons. They spoke on condition of anonymity because it is customary for changes in the government to be announced only once a vacant position is filled.

A hard-liner and ex-junta official, Tin Aung Myint Oo left his post after returning from a health checkup in Singapore and has since become a Buddhist monk, the family members said.

The 61-year-old had served as the No. 5-ranking official in the former junta who was in charge of the military's economic arm. His views were believed to be at odds with the liberal approach of Thein Sein.