Belgium will respond to the threat it faces "firmly, calmly and with dignity," King Philippe said in a televised address on Tuesday evening in the wake of the Brussels terror attacks.
"Our country is in the mourning," Xinhua quoted the king as saying in a short speech broadcast at 19:00 local time (18:00 GMT).
Describing the attacks as "cowardly and odious," King Philippe said he and his wife Mathilde shared their sorrow with those who have lost a loved one or who were injured.
He praised the work of the emergency services and gave thanks to "all those who spontaneously offered help."
King Philippe concluded: "Faced with this threat, we will continue to respond firmly, calmly and with dignity. Let us remain confident in ourselves. This confidence is our strength."