A United Nations' human rights envoy has visited Yangon's notorious Insein jail as he begins an investigation into the recent crackdown on anti-government protests.

Paulo Sergio Pinheiro, the UN's independent rights investigator for Myanmar, is on day two of his first visit to the country in four years.

He said he wants to find out exactly how many people were killed or detained during September's crackdown.

The official death toll stands at 10, but activists and diplomats based in the country say the number of dead was much higher, while many more remain in detention.

Also on Monday Pinheiro visited a Buddhist monastery raided by troops during September's crackdown on anti-government protests.

Pinheiro also met with officials at the Religious Affairs Ministry and the Home Affairs Ministry where he discussed his proposed visits to prisons.

A proposed itinerary was given to Myanmar's military rulers before the visit began on Sunday, but it was still being "fine-tuned," said Aye Win, the UN spokesman in Myanmar.

Pinheiro has a history of difficult relations with Myanmar's ruling generals and has not visited the country in four years.

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

He has been barred from the country since November 2003.