YANGON - Myanmar opposition leader Aung San Suu Kyi pleaded not guilty at her trial on Friday and blamed the regime's lax security for allowing an American intruder to swim uninvited to her lakeside home, her lawyers said.

The closed court in Yangon's notorious Insein Central Prison formally charged the Nobel laureate, her two female housemates and the U.S. man after five days of hearings that have sparked international outrage.

Are you guilty?, the presiding judge, U Thaung Nyunt, asked the 63-year-old Suu Kyi.

No, because I did not commit any crime, she calmly replied, according to her lawyer Nyan Win.

Suu Kyi faces up to five years in jail if found guilty of breaking the terms of her house arrest by allowing the American, John Yettaw, to stay in her home for two days in early May.

She told her lawyers on Friday she was responsible for allowing him to stay on humanitarian grounds. She had asked him to leave, but Yettaw said he was too exhausted.

Suu Kyi blamed the regime for lax security at her home, where she has spent most of the past six years under police guard, with her phone line cut and visitors restricted.

If the security had been proper, he would not have got here, Suu Kyi later told her lawyers.

The court formally charged Suu Kyi and her two female housemates for violating her house arrest under a draconian security law.

Yettaw pleaded not guilty to breaking the same law, immigration violations and a charge of illegal swimming.

I am not guilty because I had a dream about the assassination of Aung San Suu Kyi and I came to warn her, Yettaw was quoted as telling the judge.

When the judge asked the 53-year-old American why he had swum to Suu Kyi's home, he replied: I swam there because I could not walk on water.

Friday's hearing took a bizarre turn when Yettaw rose to his feet, turned away from the judge and told the courtroom: She is innocent. She is not guilty. He then sat down.

ELABORATE PLOT

Critics have denounced the trial as a ploy to keep Suu Kyi, the charismatic National League for Democracy (NLD) leader, in detention until after 2010 elections. The West derides the polls as a sham to entrench nearly a half century of military rule.

In the first comments on the trial from a senior junta official, Foreign Minister Nyan Win suggested the incident at Suu Kyi's home was an elaborate plot by anti-government elements.

The foreign minister, who goes by the same name as Suu Kyi's lawyer, said the incident was probably trumped up to intensify international pressure on Myanmar at a time when the United States, Japan and some European countries were reviewing their policies toward Myanmar, state media reported.

The United States has renewed sanctions against the regime while it conducts its review. The European Union has threatened tougher measures since Suu Kyi was charged a week ago.

The junta's mouthpiece, the New Light of Myanmar, published details of Thursday's hearing, which was closed after diplomats and journalists were allowed inside the prison court on Wednesday in a rare concession from the regime.

The court was shown pictures and video footage taken by Yettaw inside Suu Kyi's home, where she has been a virtual prisoner for more than 13 of the past 19 years.

Police Major Aung Htut Kyaw said the Canon camera seized from Yettaw contained 331 photos and one video file. They showed the flippers, Yettaw in disguise, and Suu Kyi's home.

On the video, Yettaw said he asked Suu Kyi's permission to take photos of her and upload them on the YouTube website.

He thought she refused because she was frightened, the newspaper said in its account of the hearing.

The Missouri resident said he had left his family behind, believed God was with him and admired Suu Kyi and did not blame her for not allowing him to take her photos.