YINCHUAN - Police in northwest China's Ningxia Hui Autonomous Region on Friday evening captured a man suspected of murdering seven members of his family, including his pregnant wife and two young nieces.

Ma Yongdong, 24, has confessed to the murders, said officials with the public security department of Ningxia and the public security bureau of Pengyang County.

Ma was captured at 8:30 p.m. in the city of Wuzhong, four days after he allegedly killed his wife, his parents in-law, grandparents in-law and two nieces aged three and one in their home in Pengyang County on October 14, according to police.

The murders happened after Ma had an argument with some of the victims that afternoon, according to the suspect's relatives.

Police did not release any other information, saying the investigation is still underway.

Ma Yongdong (L) answers questions to officials with the public security bureau of Pengyang County, Ningxia Hui autonomous region, Oct 18, 2013. [Photo/CFP]