The operation marks the first phase of a broader agreement between Malaysia and Myanmar that could eventually see as many as 5,000 people returned.

Malaysia’s government maintains that the repatriations are voluntary. However, the U.N. refugee agency and civil society groups have questioned whether safe and voluntary returns are possible while Myanmar remains engulfed in armed conflict.

According to Malaysia’s Home Ministry, 1,476 Myanmar nationals were included in the first group. They consisted of 1,370 men, 79 women, 20 boys and seven girls, ranging in age from 8 to 60.

Dozens of buses accompanied by security vehicles transported the group Tuesday morning to the Lumut naval base in Malaysia’s Perak state. Two Myanmar naval vessels and a hospital ship were deployed for the operation.

Malaysia’s Home Ministry said the Myanmar government identified those eligible for repatriation and that the individuals had agreed to return. Malaysian authorities previously said those selected for the first phase had signed documents confirming their consent.

The government said additional phases would proceed following identification, documentation and verification procedures.

Human rights groups have urged Malaysia to halt the program, warning that returnees could face violence, persecution or forced conscription amid Myanmar’s continuing conflict. More than 160 civil society organizations called on Malaysian authorities last week to stop the planned returns.

The U.N. refugee agency has also raised concerns about the safety of those being returned and said it was not involved in the repatriation process.

Malaysia hosts a large population of refugees and asylum seekers from Myanmar, including ethnic Rohingya, Chin, Karen and Mon communities. The government says the phased repatriation program is intended to provide a structured process for those who voluntarily agree to return.