Belgium's King Philippe addressed the UN Security Council in New York on Wednesday, making a rare appearance by a sovereign and calling for better protection of children in conflict zones.

"Today, one in five children worldwide is negatively affected by armed conflict," he said, adding the figure "represents girls and boys fleeing combat, mutilated, exploited, killed, victims of sexual violence or recruited by armed groups."

"All too often the plight of children remains overlooked. Their voices, rights and needs are barely taken into account."

King Philippe, 59, was accompanied by Queen Mathilde, the honorary president of UNICEF Belgium.

A Belgium monarch has spoken before at the UN General Assembly, but King Philippe was the first Belgium king to address the UN Security Council, which the country is chairing in February.

At the meeting, the Security Council unanimously approved a declaration condemning violations of international law related to children, including the recruitment of children in armed conflict and attacks on schools.