A UN human rights envoy has asked to visit Mynamar's Insein prison, where hundreds of pro-democracy activists are held, during a six-day visit to the country.
Tomas Ojea Quintana's visit comes after Aung San Suu Kyi's opposition party urged the UN to take action against human rights abuses in military ruled Myanmar.
"The main objectives of his visit are to assess the development of the situation of human rights since his previous mission last summer," the office of the UN High Commissioner for Human Rights said in a statement.
On Sunday, Quintana was visiting the eastern Karen region, along the border with Thailand, where separatists have been fighting for autonomy since 1949.
He also plans to travel to western Rakhine and northern Kachin states.
Rakhine is home to hundreds of thousands of Rohingya, a Muslim ethnic group not recognised by Myanmar.
Hundreds of Rohingya who recently attempted to flee Myanmar and camps across the border in Bangladesh were allegedly mistreated after being picked up by the Thai military.
Suu Kyi meeting
Quintana is also expected to meet Suu Kyi after two leaders from her National League for Democracy (NLD) party were reportedly jailed without trial and another had his sentence extended.
Nyipu and Tin Min Htut have each been sentenced to Insein prison for 15 years, Nyan Win, spokesman for Suu Kyi's National League for Democracy.
"They were charged with three offences including the electronic act," Nyan Win said, referring to the regime's ban on unauthorised use of computers.
The two men were arrested in August after they wrote an open letter to the UN criticising the ruling generals' seven-step roadmap toward democratic political changes.
The NLD vice-chairman, 82-year-old Tin Oo, is to remain under house arrest for at least another year, said Nyan Win, spokesman for Suu Kyi's National League for Democracy.
Tin Oo was arrested with Suu Kyi in May 2003 after an attack on their motorcade during a political tour.
The opposition party launched a petition on Thursday, calling for the release of all political prisoners including Suu Kyi and Tin Oo.
Suu Kyi won a landslide election victory in 1990 that the military government refused to recognise. She has been under house arrest for more than 13 of the last 19 years.
Long jail terms
The military regime has handed out heavy jail terms of up to 104 years to dozens of pro-democracy activists in recent months.
Criticis have said that the jailing of political activists is an attempt to clear away dissent prior to general elections promised for 2010.
Quintana's visit comes less than two weeks after a visit by Ibrahim Gambari, the UN special envy to Myanmar.
Recommendations following his previous visit include reforms of legislation to ensure
human rights protection, the release of political prisoners, independence for the judiciary and training on human rights for the army.
Quintana's visit could pave the way for a possible visit later in the year by Ban Ki-Moon, the UN secretary general.