Chinese police have detained six people for beating to death a woman at a McDonald's restaurant who refused to disclose her phone number, accusing them of being members of a religious cult, state media said Saturday.

The woman became involved in an argument with the six people, including a juvenile, who then allegedly beat her on Wednesday evening in Zhaoyuan city in Shandong province, the official Xinhua news agency said.

They were seeking to recruit the woman into a "evil cult" called Quannengshen, it said.

The group, which can be translated as Church of Almighty God, is a doomsday cult which was outlawed by the government in the mid-1990s, according to media reports.

Photos circulating on social media showed the woman wearing a white shirt and blue trousers lying face down in a pool of blood. She died after being taken to hospital, Xinhua said.

The six suspects included a man, his two daughters and a son, as well as two women, it said. The case of the juvenile, who media reports said was a 12-year-old boy, would be handled separately as he was below the age of criminal responsibility.

In a separate statement released on its official China microblog, McDonald's expressed "deep-felt grief" and pledged to investigate the matter.

China outlawed another group it labelled as an "evil cult", the spiritual movement Falungong, in the 1990s and has since detained tens of thousands of members. The group says its members are tortured for refusing to give up their beliefs.