Ibrahim Gambari has called for the release of all political prisoners in Burma and voiced concern at reports of continuing government abuses in the wake of last week's protests.
Mr Gambari, addressing the UN Security Council after a four-day visit to Burma, also said there were unconfirmed reports that the number of casualties was much higher than the dozen people reported killed by the government.
The junta says 10 people were killed in the crackdown on the biggest challenge to the regime in nearly 20 years, though Western governments say the toll is likely to be far higher.
The Western powers have called for the Security Council to impose sanctions on Burma.
But veto-holding China is opposed to any action by the 15-member body because they say the junta's crackdown on pro-democracy campaigners was an internal affair.
Addressing the Council just before Mr Gambari, UN Secretary-General Ban Ki-moon called for bold actions by the military government toward democratization and respect for human rights.
The UN envoy to Burma, Ibrahim Gambari, has briefed the Secretary-General, Ban Ki-moon, about his talks with the Burmese military authorities after last week's suppression of anti-government protests.
Mr Gambari is due to address the UN Security Council in public session today.
During his four-day-visit, Mr Gambari secured the military junta's agreement to meet the pro-democracy figure, Aung San Suu Kyi, who is under house arrest.
But her National League for Democracy party has said conditions set by Burma's military leader, Than Shwe, showed he was not serious about holding direct talks with her.
Today Aung San Suu Kyi's party dismissed the Burmese junta's offer of talks as surreal.
