Eight people have been shot in Chad in the first executions since 1991.
Four men convicted of murdering a Sudanese businessman in September were among those killed by an army firing squad in the capital, Ndjamena.
The executions, witnessed by two ministers and journalists, have been condemned by human rights groups.
"We believe we are in a police state. We didn't give the suspects a chance to appeal," said Jean Padre from the Chadian Human Rights League.
Oil pipeline
The murder of Sheik Ibn Oumar Idriss Youssouf, a Sudanese executive with a Chadian oil firm, caused a scandal at a time when Chad is trying to attract foreign investment in its oil sector.
The four men were found guilty a month after his murder and executed two weeks later.
"Chad has given a wonderful example to wrong-doers," Interior Minister Routouang Yoma Golom told the AFP news agency.
Three other convicted murderers were killed at the same time in Ndjamena, while another was shot dead in the eastern town of Abeche, AFP reports.
President Idriss Deby last month launched a major new oil pipeline, partly funded by the World Bank.
Although rich in minerals like gold and oil, Chad is among the world's poorest countries.