A senior United Nations official has concluded a visit to Burma saying he sees a “historic opportunity” for change.

Vijay Nambiar, chief of staff to the U.N. Secretary-General Ban Ki-moon, released a statement Friday relaying to Burmese leaders the encouragement of Mr. Ban on steps taken toward reform. He said Mr. Ban also praises the significant efforts made by all concerned to advance national dialogue and reconciliation.

A new, nominally civilian government took office in Burma at the end of March.

During his five-day visit, Nambiar met with Burmese officials and democracy leader Aung San Suu Kyi. He also met with representatives of other political parties, with civil society organizations, and with the National Human Rights Commission.

Mr. Nambiar urged Burma to release the political prisoners who remain in detention. Reports say Burma released nearly 200 prisoners last month. Human rights groups and Western governments say Burma must release about 2,000 political prisoners before international sanctions can be lifted.

Burmese Information Minister Kyaw San told VOA's Burmese Service Friday that authorities have released 16,000 prisoners as part of mass amnesties, but he refused to acknowledge the existence of any political prisoners.

He said all prisoners are in detention because they broke the law, although some might also have been involved in politics.

Rights group Amnesty International on Friday voiced concern about prominent imprisoned Buddhist monk U Gambira, saying he urgently needs to be hospitalized and treated for injuries resulting from torture he suffered in 2009.