Three young men distributing leaflets at a fruit market in the main city of Rangoon were seized as Paulo Sergio Pinheiro prepared to hold talks with the Burmese foreign and labour ministers in the remote jungle capital of Naypidaw.

Their detention followed the arrest in Rangoon yesterday of a leading female activist, Su Su Nway, who had been on the run for a month, as she tried to post a protest leaflet near Mr Pinheiro's hotel. It also emerged that U Gambira, leader of the All-Burma Monks Alliance, had been seized.

The new round of arrests followed the UN special envoy Ibrahim Gambari's report to the security council on his second visit in as many months, in which he said the Burmese junta was making progress and that he found a ìqualitative differenceî from his previous trip.

The former Nigerian foreign minister said the 45-year-old regime had shown signs that it could be responsive to the concerns of the international community, which has roundly condemned the crackdown of the popular protests that left at least 13 dead and almost 3,000 behind bars.

He added that the regime - which last week allowed the detained opposition leader Aung San Suu Kyi to meet senior figures from the National League for Democracy - had started a process that could lead to it holding negotiations about moving toward democracy.

But sceptics in the international community doubt that the Burmese regime has altered its mindset. The US warned that the UN security council should not rule out further sanctions if Burma did not follow through on promises to Mr Gambari, who was denied a meeting the regime's leader, Than Shwe, on his second visit.

"What has happened does not reflect a fundamental shift," said the US ambassador to the UN, Zalmay Khalilzad. "We are of the view that both pressure and engagement have to be on the table ... we do not rule out sanctions.

"The military regime's so-called 'road map to democracy', which excludes Burma's democratic and ethnic minorities groups from equal participation, is demonstrably inadequate."