BEIJING: A Catholic priest and a nun were murdered in northern China this week, but the motive was not immediately clear, police said Thursday.

AsiaNews, a Vatican-based news service, said Joseph Shulai Zhang and Sister Mary Wei Yanhui were apparently stabbed to death at the nursing home where they worked in the city of Wuhai in Inner Mongolia.

After the two failed to appear at morning mass, their bodies were discovered in a pool of blood in the home, which was housed within the local church, the report said.

The priest was apparently stabbed seven times, while the nun suffered one stab wound to the chest, the report said, adding they were members of the area`s underground Catholic church.

"This is a criminal matter, we are in the process of cracking this case," a city policeman, also surnamed Zhang, told AFP.

The policeman said the motive for the murders was not immediately clear and that investigators were not sure how many suspects were involved.

Zhang, 55, had been a priest since 1985. Sister Wei, 32, was the director of the nursing home, which housed about 60 elderly people, AsiaNews said.

China has about five million Catholics who worship at Communist Party-sanctioned "official" churches, while up to 11 million reportedly worship at "underground" churches not approved by Beijing.

The vast country has witnessed a spate of violent killings in recent years, many linked to disgruntled and often impoverished farmers seeking revenge for alleged social injustices.

In recent months, China has seen a number of attacks on young schoolchildren around the country since March that have left 17 people dead, including 15 pupils, and scores injured.

BDST: 1655 HRS, July 8, 2010