Chinese man Huang Shigang, 31, and the Vietnamese Le Doan Thuy Tien, 26, Nguyen Thi Tham Trinh, 28, Vo Thanh Tai, 27, and Truong Ngoc Thien, 29, illegally held Tran Thanh Dung, 31, in the southern province of Tien Giang since he owed Huang VND350 million ($15,100), media reports said.
They are confined in their houses in Long An Province, about 50 kilometers to the north of Tien Giang, pending an investigation. Huang is prohibited from leaving Vietnam.
Dung, a dragon fruit merchant, was held on June 29 while the abductors called his wife, Nguyen Thi Kim Chung, 26, and demanded VND400 million ($17,300) for his release.
Dung had told her he was going to meet a Chinese dragon fruit merchant to talk business, but she did not know his name or address, she said.
She informed the police and went to a coffee shop in the province to pay the kidnappers. Tai was arrested while receiving the money.
He led them to the others, and the police rescued Dung.
They seized a car and more than $5,000 in cash from the gang.