YANGON: Myanmar's military regime allowed a medical assistant to enter the house of Aung San Suu Kyi on Monday, witnesses said, amid ongoing concerns for the health of the detained opposition leader.

The 63-year-old Nobel Laureate was placed on an intravenous drip at her lakeside home in Yangon on Friday because she cannot eat, has low blood pressure and is dehydrated.

Her doctor, Tin Myo Win, has been detained since last week on unspecified charges and the physician's assistant, Pyone Moe Ei, was refused access over the weekend.

But on Monday the assistant entered Aung San Suu Kyi's house at around lunchtime and was still there around three hours later, said witnesses.

There was no immediate comment from her party, the National League for Democracy (NLD), which had appealed on Sunday for the ruling junta to allow Aung San Suu Kyi to receive medical care.

The pro-democracy icon has spent most of the last 19 years in virtual isolation at the house, where she lives with two maids and receives visits only from her doctor, doctor's assistant and lawyer.

Myanmar authorities on Wednesday arrested a US national after he swam across a lake to the off-limits compound and spent two days there. State media identified him as 53-year-old John William Yeattaw.

He had slept for two days on the ground floor of Aung San Suu Kyi's house and asked the detained leader not to inform authorities he was there, official sources said.

The man's motive remained unclear but officials said he was a Vietnam war veteran.

Aung San Suu Kyi's latest period of detention expires at the end of May and authorities have not said if they will extend her sentence.

The ruling junta is holding elections next year that critics dismiss as a sham to entrench the junta's power.

The NLD won a landslide victory in elections in 1990 but the military refused to let the party assume office. Myanmar has been ruled by the military since 1962.