King Norodom Sihamoni today left Phnom Penh to begin his three-day state visit to Vietnam.
Prime Minister Hun Sen, National Assembly president Heng Samrin, Senate president Say Chhum and senior officials saw off the King at the Phnom Penh International Airport.
According to a letter issued on Tuesday, the King said that he will pay the state visit in Hanoi and Danang in Vietnam at the invitation of Vietnamese government.
He said that Mr Chhum will become acting head of state.
Last week, Mr Hun Sen paid an official visit to Vietnam, and met with Vietnamese president Nguyen Phu Trong and National Assembly president Nguyen Thi Kim Ngan.
Mr Hun Sen also had a fruitful conversation with his Vietnamese counterpart, Premier Nguyen Xuan Phuc.