Dozens of supporters of the ailing Nobel Peace Prize laureate gathered near Insein prison outside Yangon as the hearing got under way, one of whom was arrested by the phalanx of riot police posted behind barbed wire blockades.
The ruling junta pushed ahead with the trial of the 63-year-old despite the threat of tougher sanctions from the European Union over the charges against her, which allege that she violated the terms of her house arrest.
"We can definitely win according to the law. She didn´t do anything wrong," Nyan Win, a spokesman for Aung San Suu Kyi´s National League for Democracy party, told AFP after the court was adjourned.
Lawyers for the pro-democracy leader opened the proceedings with an application for the trial to be held in open court, which the judges rejected, Nyan Win said.
The court then heard from the first of an expected 22 witnesses, police colonel Zaw Min Aung, who filed the original complaint against the pro-democracy leader after the incident involving the American man, he added.
Nyan Win quoted the policeman as saying that Aung San Suu Kyi had "violated the personal restrictions on her" by having contact with John Yettaw, the man who swam across a lake to her residence earlier this month.
She was wearing traditional Burmese clothing in a dark green-blue color and did not speak during the hearing, he said. But she was "alert and wanted to tell friends that she is in good health," he added.
Her latest six-year period of detention was due to expire on May 27, but Yettaw´s visit has apparently provided the ruling generals with the ammunition they need to extend her detention past the 2010 polls.
Yettaw, 53, reportedly described as a harmless eccentric by relatives in the United States, also appeared at the trial along with two aides of Aung San Suu Kyi. A US consular official attended the hearing with Yettaw, Nyan Win said.
Yettaw used a pair of home-made flippers to swim across a lake earlier this month to the residence where Aung San Suu Kyi has been kept in virtual isolation for most of the last 19 years.
Security forces barred the ambassadors of Britain, France, Germany and Italy from the jail as they attempted to gain entry to the court, a western diplomat said.
The hurriedly arranged trial of Aung San Suu Kyi comes just days after she was taken from her lakeside property and imprisoned at a "guest house" inside the Insein prison compound.
Her lawyer, Kyi Win, said that she would protest her innocence when called on.
"She just felt sorry for this man (Yettaw) as he had leg cramps after he swam across the lake. That´s why she allowed him to stay," Kyi Win said.
Several dozen NLD members gathered outside the security cordon at the jail, including Win Tin, who was Myanmar´s longest serving political prisoner until his release in September, witnesses said.
The junta, headed by reclusive Senior General Than Shwe, has kept Aung San Suu Kyi in detention for a total of 13 years since 1990, when it refused to recognize her party´s landslide victory in Myanmar´s last elections.
The military has ruled Myanmar, formerly known as Burma, since 1962.
The European Union said Monday it would consider boosting its sanctions against the Myanmar regime after it put Aung San Suu Kyi on trial.
"We are ready to go forward," said Czech Foreign Minister Jan Kohout, whose country holds the rotating EU presidency, as he arrived for talks with his counterparts in Brussels.
US President Barack Obama formally extended sanctions against Myanmar on Friday. But there has been silence from most of Myanmar´s Asian neighbours who value its rich natural resources.
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