U.N. Secretary-General Ban Ki-moon called on Myanmar's president to address citizenship concerns for members of the long-persecuted Rohingya Muslim community.

He also emphasized the need Thursday for improved humanitarian access and better cooperation with the United Nations as it tries to help.

Myanmar, a predominantly Buddhist nation of 50 million, found itself on the defensive this week as world leaders flocked to the capital, Naypyitaw for a series of regional summits. Ban and others expressed serious concerns in private with President Thein Sein.

The country's 1.3 million Rohingya — almost all of whom live in Rakhine state — have been described by the United Nations as one of the world's most persecuted minorities. They have been denied citizenship by the national government. Their main medical lifeline, the Nobel prize-winning Doctors Without Borders, was kicked of the state eight months ago.