Every year, after Lunar New Year celebrations, Vietnam residents in Nem Thuong village, 30km north of Hanoi, traditionally carry out a public slaughtering of two well-fed pigs.
Hundreds of people, many of them children, gather to watch the pigs being chopped in half.
Villagers then dip bank notes into the freshly-spilled blood and put them on altars in their homes to wish for good health and luck.
The yearly event honours a general believed to have killed wild hogs to feed his starving soldiers after they repelled invaders, centuries ago.
This year's procession was met with opposition from Hong Kong-based animal welfare group Animals Asia Foundation.
They launched a campaign to collect signatures for stopping the festival at Nem Thuong village.
Animals Asia Vietnam said they plan to use the petition to urge Vietnam's National Assembly at its upcoming gathering in May to include a new clause in the law that would make violating animal welfare a crime.
Bac Ninh Province's culture officials recently proposed that villagers should make the festival less gory, Vietnam's Thanh Nien Daily said.
Many villagers at Nem Thuong, however, remain defiant.
In Vietnam, some residents eat dogs and cats, considered a taboo practice in the Western world. Many Vietnamese also capture bears for bile extraction.