PHNOM PENH, Nov. 21 (Xinhua) -- Cambodia began to celebrate the three-day Water Festival on Wednesday with boat races attracting tens of thousands of spectators from across the kingdom.

The annual boat race is held along a 1.7 km-stretch of the Tonle Sap river in front of the royal palace in Phnom Penh, capital of Cambodia.

Bou Chumserey, vice chairman of the boat-racing technical control committee, said about 295 dragon boats with 19,017 oarsmen took part in this year's regatta, up from 265 boats with 18,000 rowers in last year's event.

"We encourage boatmen and people to participate in the festival in order to preserve this age-old tradition," he told Xinhua.

"Boat race is to remember the strength of the powerful Khmer marine forces during the ancient Khmer Empire in the late 11th century," he said.

The festival is also to mark the end of annual rainy season and the unique reversal flow of the Tonle Sap river that connects the Tonle Sap Lake with the Mekong river, he said.

"It is to express our gratitude to the Mekong river for providing us with fertile land and abundant fish," he said.

According to Chumserey, Cambodian King Norodom Sihamoni, along with Prime Minister Samdech Techo Hun Sen and other dignitaries, will watch boat races from a stage erected on the riverbank in front of the royal palace late Wednesday afternoon.

"This is our Khmer tradition, and our Khmer kings have celebrated this boat-race festival since the ancient time until the present time," spectator Ho Khema, 20, told Xinhua.

"In the old time, boats had been used by marine forces to do war against the invading enemies," she said.

The National Police said that more than 13,000 security personnel have been deployed to ensure security and safety for the festival-goers during the three-day holiday.