About 20,000 pilgrims flocked to pay homage and pray at the Hung Kings Temple in northern Phu Tho Province on the death anniversary of the nation's mythical founding fathers Wednesday.
Many members of the crowd, masked and unmasked, used their smartphones to capture the procession.
Many people sat down on the hillside, waiting for the main worship ceremony to begin.
On a corner of the hill, soldiers used binoculars to track flying objects like drone cameras.
At 8 a.m. the crowd started flocking to the temple, prompting police and military forces to quickly divide them and prevent the situation from turning chaotic.