YANGON - MYANMAR'S junta said on Thursday that a US man on trial for swimming to the house of Aung San Suu Kyi had links with exile groups in Thailand, apparently toughening its stance ahead of a visit by a UN envoy.

The military-ruled nation's police chief for the first time named top dissidents with whom American John Yettaw had allegedly met before making the first of two visits to the democracy icon's lakeside residence.

Aung San Suu Kyi is also on trial for allegedly breaching the terms of her house arrest, over what she says were uninvited visits by devout Mormon and former US military veteran Yettaw. Both face up to five years in jail.

The junta rolled out the allegations a day before before UN troubleshooter Ibrahim Gambari was due to visit Myanmar to lay the groundwork for a planned visit by UN Secretary General Ban Ki-moon.

'According to concrete information, during Mr Yettaw's stay in Thailand he met with some people from illegal organisations,' police chief Khin Yee told a hastily arranged press conference at the interior ministry in Yangon.

He said that Yettaw had met activist Bo Kyi, co-founder of leading activist group the Assistance Association for Political Prisoners of Burma, while he was staying in the Thai border town of Mae Sot in September-October 2008.

Bo Kyi spent seven years in jail following a failed student uprising in 1988 and is an outspoken critic of Myanmar's military regime.

The regime last month said Yettaw's visits to Aung San Suu Kyi's house were organised by 'anti-government elements' and that he was a 'secret agent or her boyfriend", but has not given details of the alleged links.

The trial at Yangon's notorious Insein prison has heard that Yettaw walked through a drain to briefly visit her house in November 2008 and then swam across a lake to the house in May before staying there for two nights. -- AFP