A convoy containing her car and several police vehicles swept out of the 63-year-old's lakeside residence in the main city of Yangon just after 7.00am (0030 GMT, 8.30am Singapore time), they said.
Heavy security was in place and police sealed off the road to the house.
Witnesses said about 15 minutes later Aung San Suu Kyi's car entered the notorious Insein prison on the outskirts of Yangon, where she is due to appear in court in connection with the incident involving the American. Her party earlier said she was expected in court at 10.00am.
US national John Yettaw was detained by police in the military-ruled nation last week for gaining uninvited access to the 63-year-old Nobel Laureate's off-limits lakeside residence in Yangon and staying there for two days.
News of the charges emerged after the lawyer, Kyi Win, visited Aung San Suu Kyi at her home on Wednesday, the spokesman said. Aung San Suu Kyi has spent most of the past 19 years detained in virtual isolation in her house since the junta refused to recognise the NLD's landslide victory in the country's last elections in 1990.
Her party said at the weekend that she was in poor health and called for her to be given urgent medical assistance after her doctor was arrested for questioning over the incident with the American. Lawyer Kyi Win said last week that Mr Yettaw was an 'adventurous' American acting of his own accord.
Her latest period of detention at her home - where she lives with her maids and is permitted occasional visits from her lawyer and doctor - expires at the end of May but diplomats say it is likely the government will extend this sentence. -- AFP