Approximately 3,000 people in attendance bowed and the nation observed a moment of silence as King Norodom Sihamoni and Queen Mother Norodom Monineath lit the funeral pyre, the Phnom Penh Post reported.
Tens of thousands of people filled the streets surrounding the crematorium and royal palace to observe as much of the ceremony as they could, officials said.
The king and queen mother will spend the next two days traveling the Mekong River to spread some of the former king's ashes. The remainder of the ashes will be placed in a diamond urn, which will be stored at the royal palace, the Post reported.
Sihanouk was crowned king as a teenager in 1941. He abdicated in 2004, making way for his son to become king. He died Oct. 15 in Beijing of a heart attack at the age of 89.
2014: The Year in Fashion [PHOTOS]
U.S., allies launch airstrikes against Syria