"We issued an order of further detention," a police source said without giving further details.

The Nobel peace prize-winner's latest period of detention began in May 2003 and was set to expire this weekend.

Japanese Jiji press news agency said the junta extended the house arrest for another year, but the police source declined to comment.

An Asian diplomat in Yangon said a police car was seen entering her lakeside home here during the afternoon.

The 61-year-old Aung San Suu Kyi has spent most of the past 17 years under house arrest and has little contact with the outside world, apart from her live-in maid and visits from her doctor.

The last time the opposition leader -- the only Nobel peace laureate in detention -- was able to leave her house was November 2006, when the junta allowed her to meet visiting UN envoy Ibrahim Gambari for one hour.

The extension of her house arrest was widely expected, with observers saying the junta is fearful the hugely popular democracy leader could threaten its rule.

Aung San Suu Kyi's National League for Democracy (NLD) won a landslide victory in 1990 elections but was never allowed to govern.

Political figures from across the world have ramped up calls for her release, with ex-US president Bill Clinton and 58 other former world leaders sending a joint letter last week to junta head General Than Shwe.

Two other Nobel peace laureates -- former US president Jimmy Carter and former South Korean president Kim Dae-Jung -- were among those who signed the appeal.

US First Lady Laura Bush on Wednesday called on China, an ally of Myanmar, to join efforts to free her, saying that American women "stand with her and that we watch her and we think about her a lot."

Citing Myanmar's rights violations, including Aung San Suu Kyi's detention, the United States last week renewed sanctions against the regime for another year, as did the European Union in April.

In the past week the junta has detained at least 60 pro-democracy activists as they went to pagodas to pray for Aung San Suu Kyi's release, and 45 people, mostly NLD members, still remain in custody.

Amnesty International said Wednesday the human rights situation in Myanmar had worsened over the past the year with authorities stepping up repression of political opposition.

The United Nations has estimated there are 1,100 political prisoners in the country formerly known as Burma, which has been ruled by the military since 1962.