Supporters of Aung San Suu Kyi were angered by the court's verdict
The UN Security Council has expressed serious concern at the imposition of a new period of house arrest on Burmese pro-democracy leader Aung San Suu Kyi.
A statement from the council, which came after two days of debate, also called for the release of all political prisoners in Burma.
A court in Rangoon found Ms Suu Kyi guilty two days ago of breaking the terms of her previous house arrest.
Earlier the European Union extended its sanctions on Burma.
The EU said judges involved in Ms Suu Kyi's sentencing would now join military and government figures in having their overseas assets frozen and travel to the EU banned.
Ms Suu Kyi was found guilty because she allowed an American man, John Yettaw, to stay at her lakeside home after he swam there uninvited in May.
She was sentenced to three years in prison but the term was commuted to 18 months house arrest, ensuring the opposition leader cannot take in planned elections next year.
Governments around the world condemned the conviction.
Correspondents said Thursday's UN statement was watered down from an original US draft, which "condemned" the verdict and demanded that Burma's military junta free Ms Suu Kyi.
The main reason for the weaker language was China - a powerful permanent member of the council, with close ties to Burma's rulers, says the BBC's Tom Lane at the UN.
Together with Russia it has blocked strongly-worded condemnations in the past, our correspondent adds.
The statement, read out by the council's current president, British Ambassador John Sawers, said: "The members of the Security Council express serious concern at the conviction and sentencing of... Aung San Suu Kyi and its political impact."
Thai PM on relations with Burma
He said council members "reiterate the importance of the release of all political prisoners".
Ms Suu Kyi, 64, has spent 14 of the past 20 years under house arrest.
The US, Britain and France were among those to quickly condemn Tuesday's verdict, but Burma's neighbour China said the world should respect Burma's laws.
Meanwhile, Thai Prime Minister Abhisit Vejjajiva, who is the current chairman of the Association of South East Asian Nations (Asean) told the BBC that imposing sanctions could lead to problems and that it was important to take a balanced approach to dealing with Burma.
The latest European sanctions widen restrictions imposed on military and government members after a violent crackdown on protests in 2007.
A decade earlier, in 1996, the EU banned the sale or transfer of arms and weapons expertise to the country.
It also suspended all bilateral aid other than humanitarian assistance.
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