The Vietnamese Embassy in Angola announced Thursday that Nguyen Trong Duc, 47, and his sister-in-law Tran Thi Thu Huong, 40, both from the central province of Ha Tinh, were stabbed to death by a group of robbers in their rented apartment around 2 a.m.

Local police are investigating the robbery about which no further details have been revealed.

Nguyen Huy Hai, a police officer in Ha Tinh, said the victims’ families are working with the embassy to bring the bodies of two Vietnamese workers back home.

Ha Tinh authorities said they did not have any information on Duc's status as he had been a migrant worker in Binh Duong Province, southern Vietnam, for 10 years.

Huong was going through a tough time after her husband died in a traffic accident nearly a year ago, and her two children were being raised by her mother.

A worrying number of Vietnamese workers have been killed in Angola, a south central Africa country, by robbers in recent years. In 2017, 38-year-old female worker Nguyen Thi Dao was stabbed to death by a group of robbers. A year earlier, two male Vietnamese workers from Ha Tinh were also killed by armed robbers.

In all these instances, no information has been released on the investigations and their results.

Vietnamese recruitment firms received licenses to send workers to Angola in early 2014, but tens of thousands of Vietnamese are working there on short-term, unofficial contracts, mostly in the construction industry.