An annual dog meat festival in southern China has gone ahead, despite facing the largest-ever campaign to stop it.

An estimated 10,000 dogs are expected to be slaughtered for their meat at the Lychee and Dog Meat Festival in Yulin over just two days.

The dogs, many of which are suspected to be stolen pets or guard dogs, are slaughtered by hundreds of meat vendors in the city.

A social media campaign with the hashtags #StopYuLin2015 and #itsnofestival has attracted international attention, with celebrities including Ricky Gervais calling for the festival to be stopped. An online petition has received more than three million signatures.

Within China, there is also an increasingly powerful dog welfare movement which is beginning to change attitudes.

According to local media reports, one woman named Yang Xiaoyun paid nearly 7,000 yuan (€993) to "buy back" and save 100 dogs at the beginning of the festival.

Eating dog meat is an ancient tradition in some parts of China. Dog meat is said to be particularly warming to the body as it contains many nutrients.

Meat from stolen animals?

Dog meat is by no means widely available in China, and festivals like Yulin are exceptions. But in some provinces and among some people, dog meat remains a delicacy.

Organisers and vendors at the festival have dismissed calls for them to stop the slaughter, claiming the animals are killed humanely, and that eating dog is no different from eating pork or beef.

But there is evidence that many of the dogs are stolen rather than farmed, and are killed with clubs in particularly unpleasant slaughterhouses.

Animals Asia, a welfare charity, conducted a three-year undercover investigation on the issue, and said it had never come across any large-scale dog farms, which suggests many animals are stolen.

CEO Jill Robinson said: "Our investigations strongly point to what everybody familiar with the industry has long suspected - that the vast majority of China’s dog meat comes from stolen companion animals, and that misinformation and illegality is rife at every stage of the industry supply chain."

Traders at the Yulin Festival have been bombarded with text messages over the past few days encouraging them to cancel the festival, and the pro-animal lobby's efforts have also been reported on social media.

An ongoing poll, published by the Xinhua State News Agency, said 87.9% of the 4,606 Chinese who had responded by Sunday thought China should enact laws to prohibit animal abuse, while 12.1% say such laws were not necessary.