YANGON - Myanmar faced growing isolation over the trial of Aung San Suu Kyi Monday, as the European Union called for the release of the democracy icon and the junta lashed out at regional criticism of the case.

As the trial entered its second week, the military regime gave an apparent concession in response to the mounting international pressure when it said it would reopen the court to journalists for one day.

But the ruling generals launched a fierce outburst at the Association of Southeast Asian Nations (ASEAN) after it expressed "grave concern" over the treatment of the Nobel Peace Prize winner in a rare rebuke to Myanmar.

State media said the regime had accused neighbouring Thailand, which issued the statement one week ago as the rotating chairman of the 10-member bloc, of meddling in Myanmar's domestic politics.

"This statement... -- which is not in conformity with ASEAN practice, incorrect in facts, interfering in the internal affairs of Myanmar -- is strongly rejected by Myanmar," the New Light of Myanmar newspaper said, quoting a government statement.

The statement "sadly noted" that Thailand had "failed to preserve the dignity of ASEAN, the dignity of Myanmar and the dignity of Thailand".

Aung San Suu Kyi faces up to five years in jail if convicted of breaching the terms of her house arrest after an eccentric American, John Yettaw, swam to her lakeside house.

Yettaw has told the trial that he wanted to warn her that she would be assassinated. He used a pair of home-made flippers and a plastic bottle to make the night time water journey earlier this month.

A Myanmar official said 10 local journalists and 11 representatives from foreign media would be allowed to attend the trial at the notorious Insein Prison near Yangon on Tuesday.

The regime also unexpectedly opened up the court last Wednesday to media and foreign diplomats but it was not immediately clear if envoys would be given access on Tuesday.

Myanmar's broadside came as the European Union urged called at an Asia-Europe (ASEM) Foreign Ministers' Meeting in Hanoi on Monday for the "immediate release" of Aung San Suu Kyi.

The message was conveyed to Myanmar Foreign Minister Nyan Win on the sidelines of the meeting, said Czech Foreign Minister Jan Kohout, whose country holds the rotating EU presidency.

But Kohout acknowledged that "I don't have a positive feeling" about the chances of the 63-year-old campaigner going free.

British junior foreign minister Bill Rammell urged ASEM to issue a "very strong statement" on the issue, while Japanese foreign ministry spokesman Kazuo Kodama said Tokyo had "a deep concern with the situation".

Separately EU external relations commissioner Benita Ferrero-Waldner told reporters on Monday in Bangkok the ASEAN statement last week was "remarkable".

In Bangkok, a government spokesman defended its decision to issue the statement and said that it "does not interfere in the internal affairs of Myanmar".

The Southeast Asian bloc has come under pressure from the United States and the EU to exert its influence on Myanmar, which has kept Aung San Suu Kyi in detention for 13 of the past 19 years.

Critics of Myanmar's regime have accused it of trumping up the charges as an excuse to keep Aung San Suu Kyi in jail ahead of controversial elections promised by the ruling generals in 2010.

The activist's party won elections in 1990 but was never allowed to take power by the military, which has ruled Myanmar since 1962 and holds more than 2,000 political prisoners.

State media meanwhile reported that Myanmar officials had blamed "terrorists-cum-insurgents" after a timebomb was found on a train in the administrative capital Naypyidaw on Sunday.