YULIN, China - Residents of China's southern city of Yulin defended eating dog meat to celebrate the summer solstice on Thursday, as animal rights activists seek new ways to pressure organizers to cancel the annual festival.

The ten-day event, dubbed the lychee and dog meat festival by residents, has become a lightning rod for dog lovers, who every year confront those who buy, sell and eat canines.

In recent years, animal rights activists have raided slaughterhouses and intercepted truckloads of dogs in efforts to limit the number of animals killed.

Activists say the dog meat trade is inhumane and unhygienic, pointing to videos of dogs caught with wire lassos, transported in tiny cages and slaughtered with metal rods.

Festival-goers remain defiant.

"Yulin's so-called lychee and dog meat festival is just a popular custom of ours. Popular customs themselves cannot be right or wrong," Yulin resident Wang Yue told Reuters.

"Those scenes of bloody dog slaughter that you see online, I want to say that the killing of any animal will be bloody. I hope people can look at this objectively."

Dog meat is a traditional food in some areas of southern China, where it is believed to be good for the body in warm weather.

However, animal protection group Humane Society International said in a statement the festival was "manufactured" by the dog meat traders and that dog meat was not part of mainstream food culture in China.

The event is not sanctioned by Yulin authorities, but police told Reuters their efforts to "maintain stability" had reduced the number of activists in the city this year.

Opinions on Chinese social media were divided.

Calls from animal lovers to boycott or cancel the festival provoked a defence of local tradition and accusations that activists were disturbing public order.

International animal rights groups say putting pressure on the dog meat trade has become harder after China stepped up scrutiny of foreign groups by requiring them to register with police.

Chinese activists are trying new tactics to convince authorities to end the dog meat trade.

Zhang Huahua, a university professor at the South China University of Technology in Guangzhou province, complained to Yulin authorities that the festival infringed environmental protection regulations.

"The messy slaughter of numerous dogs transported to Yulin without inspection severely damages public order, popular custom and the environment," Zhang said in a letter seen by Reuters.

Authorities told Zhang her letter would be processed in line with regulations.