Police in the southern province of Binh Duong near Ho Chi Minh City on Sunday arrested six suspects in the fatal shooting of a company director last Friday evening.
They did not reveal the detained suspects' identities.
A Thanh Nien source said the mastermind behind the shooting was Pham Tuan Thanh, director of Hai Nam Phat Limited Company, which makes cashewnut products.
Thanh is suspected of hiring assailants to shoot 40-year-old Phan Van Lan, the director of a company who owed him VND450 million (US$21,850), the source said.
Thanh, 32, had fled his home in Ben Cat District when police surrounded the place last Saturday. A warrant has been issued for his arrest.
The victim, Phan Van Lan, 40, director of Lan Thao Company, which supplies iron and steel for roofing, was shot dead a day earlier by a hit man that Thanh had hired, the Thanh Nien source said.
Witnesses said a group of people had come to the office of the Lan Thao company in Thu Dau Mot Town at around 11 a.m. on the same day, but were chased away by the company employees.
Thanh and Hoang Xuan Hieu, his father-in-law, also the director of a local company, and a group of around 15 men later returned to the company in two cars and two motorbikes.
Two of the men went into the office and smashed the computers. When Lan returned home and asked the men why they had damaged his property, one man immediately shot at him with a gun.
The group quickly fled the scene, leaving behind a four-seater believed to belong to Thanh's father-in-law Hieu, who was on Sunday summoned by the police for questioning.
Hieu claimed he had driven to the scene in an attempt to stop Thanh from attacking Lan. He also claimed he had made a few phone calls to the police while driving.
Hieu said he had not been able to contact Thanh on his cell phone.
Thao, Lan's wife, said that she and her husband had agreed to sell a land plot of 3,000 square meters in Ben Cat District to Thanh in 2009 for VND3 billion ($145,666).
After depositing VND2 billion, Thanh decided not to buy the land and demanded his deposit back.
Thao and Lan paid him VND1.55 billion, saying they would pay the remaining VND450 million after they sold the land to a new buyer.
"However, Thanh did not agree and constantly pressured us to return the money. They had taken some gangsters to my house to threaten us more than a month ago," she said.