Daw Aung San Suu Kyi---European governments demanded her immediate and unconditional release

PARIS — Within moments of the sentencing of Myanmar’s pro-democracy leader, Daw Aung San Suu Kyi, to an effective 18 months house arrest on Tuesday, European governments demanded her immediate and unconditional release, threatening stricter sanctions against the military regime there to restrict arms supplies and curb its trade with the outside world.

The European Union demanded her freedom in a statement issued by Sweden, which currently holds the rotating presidency of the 27-nation body. In a statement, the body said it was ready to impose “targeted measures against those responsible for the verdict” and to stiffen some earlier measures, including an arms export ban, visa restrictions and financial sanctions.

In many parts of the world, her trial has been followed closely and her cause has been embraced by a broad range of politicians and human rights advocates.

“Citizens across the globe are asking world leaders to hold this brutal regime to account,” said Ricken Patel, director of an online campaign network called Avaaz.org. “Aung San Suu Kyi ’s detention today on spurious charges removes any shred of legitimacy.”

Irene Khan, the Secretary General of Amnesty International, said in a statement in London that, while the Myanmar authorities “will hope that a sentence that is shorter than the maximum will be seen by the international community as an act of leniency”, it “must not be seen as such.”

Mrs. Aung San Suu Kyi “should never have been arrested in the first place. The only issue here is her immediate and unconditional release,” Ms. Khan said.

It was not immediately clear how Myanmar’s Asian neighbors would react. Asian nations generally react cautiously to events in Myanmar, though they do sometimes offer critical comments. Analysts said that, in this instance, they may be willing to accept Myanmar’s protestations of leniency.

President Nicolas Sarkozy of France, however, called the sentencing “brutal and unjust” and said European sanctions should target profitable industries including timber and ruby mining. The French foreign minister, Bernard Kouchner, said in a statement the European Union should impose new sanctions aimed at the Myanmar leadership “and sparing the civilian population, which we should continue to protect and assist.”

In Britain, Prime Minister Gordon Brown said he was “saddened and angry” at her sentencing and said it was designed by the ruling military leaders of Myanmar, formerly known as Burma, to keep her out of elections next year.

In a statement, he said: “It is further proof that the military regime in Burma is determined to act with total disregard for accepted standards of the rule of law in defiance of international opinion.”

Calling on the United Nations Security Council to impose a global prohibition on arms sales, he added: “The facade of her prosecution is made more monstrous because its real objective is to sever her bond with the people for whom she is a beacon of hope and resistance.” France also called for an arms embargo.

The American response was likely to express similar outrage, and it seemed unlikely that the military’s decision to commute her sentence from an initial three years hard labor would soften western perceptions that the trial had been a political maneuver.

The Obama administration has been reviewing American policy toward Myanmar since February, when Secretary of State Hillary Rodham Clinton declared that the existing sanctions against its military-run government had been ineffective.

At a meeting of the Association of South East Asian nations in Thailand last month, Mrs. Clinton spoke in unusually detailed terms in discussing the country’s human rights record and its treatment of Mrs. Aung San Suu Kyi.

“We are deeply concerned by the reports of continuing human rights abuses within Burma,” she said at the time, “and particularly by actions that are attributed to the Burmese military, concerning the mistreatment and abuse of young girls.”

She also dismissed the charges against Mrs. Aung San Suu Kyi as ”baseless and totally unacceptable” and said an improvement of ties with Washington depended on the Myanmar junta’s handling of human rights issues.

”Our position is that we are willing to have a more productive partnership with Burma if they take steps that are self-evident,” she said.

Seth Mydans contributed reporting from Bangkok, and Steven Erlanger from Paris.