MANDALAY • The Myanmar police announced yesterday that they had arrested four people over the killing of a prominent Muslim human rights lawyer who was an adviser to Ms Aung San Suu Kyi - a death that raised new concerns about the country's rocky transition to democracy.

The lawyer, Mr Ko Ni, was shot in the head while leaving Yangon International Airport on Sunday.

The brazen killing comes as Myanmar struggles to emerge from decades of military dictatorship and grapples with sectarian violence between Buddhists and Muslims.

The police said they had arrested Myint Swe, whom they accuse of masterminding the killing, near the Thai border. Kyi Lin, who is accused of being the gunman, was arrested shortly after the shooting. They did not identify the other two in custody.

Officials did not disclose a motive, but the president's office said on Monday that the killing was carried out to "undermine the country's stability".

Mr Ko Ni, a member of the governing National League for Democracy, was killed as he returned with other government officials and civic leaders from Indonesia, where they had discussed democracy and conflict resolution.

Myanmar has been confronted by rising sectarian violence between the majority Buddhist population and minority Muslims, with Ms Suu Kyi, a Nobel Peace Prize laureate, facing criticism for not taking stronger action to stop attacks against the Rohingya, a Muslim minority, in Rakhine state.

The funeral on Monday for Mr Ko Ni, 65, who was involved in the interfaith peace movement, drew thousands of mourners, though Ms Suu Kyi did not attend.

While her party won a strong victory in democratic elections in 2015, the military still holds considerable power and has been accused of carrying out a brutal counter- insurgency campaign against the Rohingya. NYTIMES