Police in Yibin, Sichuan province, arrested four suspects who they say demanded a ransom of 100 million yuan ($15.7 million) in the abduction of a businessman.

The kidnappers also "forced him to kill a female masseuse and filmed the killing with the intention of using the video to coerce him to pay", said an official in the city government with knowledge of the case who asked not to be named.

About half a year ago, the authorities allege, Liu Qiang, a 39-year-old from Boxi township in Yibin who had lost money in his business, started plotting with two men and a woman to kidnap Zhang Yingqi, 53, the legal representative of the Yibin Yili Group, whose business ventures included chemical products, hydroelectric resources and real estate development.

Last week, Liu and the two men kidnapped Zhang from an elevator in his residence building and took him to a rented house in the city's Cuiping district, according to the government source.

In the rented house, Liu and the three accomplices threatened Zhang with a homemade handgun, demanding a ransom of 100 million yuan before March 2016. Zhang agreed, the source said.

Fearing Zhang would break his promise, the four kidnappers told Zhang he would be killed if he did not kill a 23-year-old woman masseuse they had abducted, the source said.

Threatened with death if he did not kill the woman, Zhang strangled her with a rope, the source said, and the process was filmed to blackmail him, the source said.

Zhang was set free, and he reported the case to the police around 4 am the next day. About nine hours later, Liu and his three accomplices were captured. The police confiscated the homemade gun and more than 50 rounds of ammunition. They also found the body of the dead woman, which had been burned by Liu and his accomplices, the source said.