UN human rights expert Paulo Sergio Pinheiro is due today to start his first visit to Myanmar in four years as rights groups demanded the ruling junta release all political prisoners.
Pinheiro had been refused entry to the country since 2003 but had repeatedly requested access, especially after a deadly crackdown on anti-government protests in September.
The Brazilian rights expert earlier this week welcomed the generals' invitation as a "positive indication" of their desire to cooperate during his Nov. 11 to Nov. 15 visit, which comes amid apparent signs of progress on establishing dialogue between the junta and democracy leader Aung San Suu Kyi.
Rights groups said Pinheiro's visit was a chance to push the generals on reforms and they demanded the release of all political prisoners.
Amnesty International wrote on Friday to Myanmar's authorities with a briefing paper outlining "grave and ongoing human rights violations" committed since the start of the clampdown, which sparked international outrage.
Amnesty estimated 700 political prisoners were still in detention, including 91 detained during the recent protests and accused the Mynamar authorities of the enforced disappearance of at least 72 people.
The government said 10 people died in the protests and about 3,000 were detained, but diplomats put both figures at far higher.
The authorities must "immediately and unconditionally release all of those who were arrested for exercising their right to freedom or expression or assembly during the crackdown, as well as all prisoners of conscience held before the recent events," the London-based group demanded.
Amnesty also called on the generals to cooperate with Pinheiro and deliver "concrete human rights improvements."
Human Rights Watch echoed its call and said the UN Security Council should "redouble efforts to prod Burma's [Myanmar] generals into starting a genuine political dialogue and ending human rights abuses."
"The government must accord Pinheiro full and unfettered access to detention facilities and account for all those detained and missing since the protests," Brad Adams, Asia director at Human Rights Watch, said in a statement. "Anything less should lead to Security Council censure."
Pinheiro's visit follows hard on the heels of a six-day mission by UN special envoy Ibrahim Gambari, who pressed the generals to establish a dialogue with detained opposition leader Aung San Suu Kyi.
In an apparent sign of progress, Aung San Suu Kyi on Friday again met a junta official and also members of her political party, the National League for Democracy (NLD), for the first time since 2003.
The Nobel peace laureate, who has spent 12 of the past 18 years under house arrest, was optimistic after the meetings and believed it was time for the "healing process" to start, her party said.
"Daw Aung San Suu Kyi said she believed the ruling authorities have the will for national reconciliation," NLD spokesman Nyan Win said in a statement after the meetings.
"Daw Aung San Suu Kyi said the bad events in September and October were sorrowful, not only for the NLD, but also for the government and the people," he said. "She said we have to work for the healing process first."
The pro-democracy protests began in mid-August after a massive hike in the price of everyday fuel, but escalated into the biggest threat to the generals in nearly 20 years when Buddhist monks emerged to lead the movement.