The United Nations secretary-general is warning Myanmar that stability in its most sensitive region can't be achieved unless it addresses the issue of citizenship for minority Rohingya Muslims.

Ban Ki-moon told a Myanmar delegation Friday that the U.N. has seen "already troubling signs of ethnic and religious differences being exploited" as elections approach later this year.

The predominantly Buddhist nation recently emerged from a half-century of military rule, but it has been shaken by violence between Buddhists and Muslims.

Most Rohingya are not citizens, and prejudice against them is high. The government calls them Bengali and generally regards them as illegal immigrants from neighboring Bangladesh, even though many were born in Myanmar.

Ban says the tensions "could be seriously destabilizing" and could jeopardize the country's efforts to reform.