'I hope that I will have a very productive stay,' he told reporters after arriving in Yangon yesterday.

He is on a mission to get inside the country's prisons to determine the number of people killed and detained since the regime's crackdown on prodemocracy protesters in September.

The media in Myanmar say 10 people were killed when soldiers were sent in to end the biggest protests in 20 years, although Western governments say the real total is almost certainly far higher.

Mr Pinheiro gave no details of his itinerary, saying it was still being discussed.

But a government official, speaking on condition of anonymity, said Mr Pinheiro will first visit Bago, a town 80km north of Yangon.

Buddhist monasteries in Bago were among those targeted in the crackdown after monks joined anti-government street protests.

The official said Mr Pinheiro will travel today to the new capital Naypyidaw, where he will meet the foreign and labour ministers, a human rights committee and the Prime Minister before returning to Yangon on Wednesday.

He is due to leave the country on Thursday.

The human rights envoy has submitted a list of prisons and detention centres he wants to visit during his five-day trip.

He warned before his trip that he would leave immediately if the junta did not accede to his demands.

'If they don't give me full cooperation, I'll go to the plane and I'll go out,' he said.

Mr Pinheiro has a history of prickly relations with the ruling generals.

He abruptly cut short a visit in March 2003 after finding a listening device in a room at a prison where he was interviewing political detainees.

Later that year, he accused the junta of making 'absurd' excuses to keep political opponents in prison.

Since then, the Brazilian envoy had been refused entry to the country despite repeated requests, especially after the crackdown on anti-government protests in September.

But an aide to the envoy said the junta, responding to international outrage at their suppression of the monk-led protests, showed 'cooperative engagement' by granting Mr Pinheiro a rare visa to visit the country.

Rights groups said Mr Pinheiro's visit was a chance to push the generals on reforms and to demand the release of all political prisoners.

The visit comes after a six-day mission by UN special envoy Ibrahim Gambari.

Professor Gambari had pressed the generals to establish a dialogue with detained opposition leader Aung San Suu Kyi.

As a result of Prof Gambari's trip, Ms Suu Kyi was allowed to meet the leaders of her opposition party on Friday for the first time in three years.

Meanwhile, Singapore is holding informal consultations with India on the situation in Myanmar.

A Foreign Ministry statement said Foreign Minister George Yeo is now in India for talks with Indian Minister of External Affairs Pranab Mukherjee.

AGENCE FRANCE-PRESSE, ASSOCIATED PRESS, REUTERS