A senior British official has called for the release of all political prisoners in Burma during the first day of his visit to the country.

Andrew Mitchell, Britain's international development secretary, met with President Thein Sein and other leaders Tuesday in Burma's administrative capital Naypyitaw. He welcomed the government's talks with opposition leader Aung San Suu Kyi who marked the first anniversary of her release from detention Monday.

But he asked for the release of about 600 more, including a rights activist who was arrested about for years ago.

The British daily Telegraph identified the activist as Min Ko Niang, a leader of the 1988 student democracy movement. Min was arrested in 2007 after leading a protest against a fuel price increase.

Human rights groups have expressed skepticism over claims by Burma's new human rights commission that as few as 300 of the nation's suspected 2,000 political prisoners are still incarcerated.

A Thailand-based rights group told VOA's Burmese service it is aware of more than 1,600 political prisoners still in jail in Burma. Amnesty International researcher Benjamin Zawacki told VOA on Monday that Burmese authorities should release the names of the remaining prisoners so the list can be cross-checked against those still believed to be jailed.

Rights group Burma Campaign in Britain urged Mitchell to do more to ensure that British aid reaches internal refugees who have fled attacks by the Burmese army in recent years.

The group says that 40 percent of Burma's population are people from different ethnic groups whose demands for more autonomy have been quashed by military force. Burma Campaign says that government attacks against civilians in ethnic states in Burma's border region have turned the conflict into the longest running civil war in which the army has committed serious war crimes and crimes against humanity.