Reports from the capital, Rangoon, said Ms Suu Kyi, who has been held incommunicado by the regime for three and a half months, had been admitted to the hospital late on Wednesday. Doctors operated on her the next day and reportedly said the surgery was a success. She was treated by her personal physician, Dr Tin Myo Win.
Security at the private Asia Royal Cardiac and Medical Centre in Rangoon has been tight, with police and the military keeping watch. Doctors and nurses were ordered to keep quiet about the 58-year-old's presence.
With mystery surrounding Ms Suu Kyi's condition - a Japanese news agency said the operation was on her uterus - her supporters say they are worried about a possible setback to her health.
"We're concerned because she's never had this kind of problem before," said Soe Aung of the National Council for the Union of Burma, an exiled pro-democracy group.
This was the first public sighting of Ms Suu Kyi since pro-government thugs ambushed her convoy on a country road in northern Burma. She was taken away after the attack and placed under "protective custody".
This month the US state department claimed she was on a hunger strike in protest at her detention, provoking denials from the Burmese authorities. Red Cross officials who have since met her say she is not refusing food.
