Yangon - Myanmar opposition leader Aung San Suu Kyi is in poor health and on a saline drip after the arrest of her private doctor last week and an unexpected visit from a US swimmer, it was disclosed Monday.

Authorities allowed Dr Pyon Mo Ei to visit Suu Kyi Monday afternoon, after arresting her other private doctor Tin Myo Win on Thursday.

Suu Kyi, 63, was described as weak and on a drip infusion, sources who requested anonymity, said.

According to Pyon Mo Ei, Suu Kyi had lost her appetite and had not eaten properly for three or four days.

Tin Myo Win was arrested Thursday, apparently for interrogation over Suu Kyi's uninvited guest, US national John William Yethaw, 53, who reportedly swam to Suu Kyi's house on Inya Lake on May 3, and stayed there until swimming back on Wednesday, when he was arrested in the lake.

Tin Myo Win was still under detention on Monday.

Suu Kyi has been under house arrest at her family compound in Yangon, which rims Inya Lake, since May 2003. She has been kept in near complete isolation for the past six years, with only weekly visits by her doctors allowed and occasional visits by United Nations special envoys.

Only her two servants have permission to stay in the house.

Suu Kyi, the only Nobel Peace Prize laureate currently under detention, was also interrogated Thursday about Yethaw's visit.

She reportedly told authorities that she deemed the visit "illegal" and "unacceptable," and had kept Yethaw downstairs in her home-cum-jail for the entire time, sources said.

Suu Kyi has spent 13 of the past 19 years under detention in her family's Yangon compound.

Suu Kyi is the daughter of Aung San, an independence hero who was assassinated in 1948. She returned to Myanmar in 1988 to tend to her ailing mother and became caught up in the country's nascent pro-democracy movement, of which she swiftly became a leading figure. (dpa)