Reports from northern Mozambique say more than 30 bodies have been found on a road in the gas-rich province of Cabo Delgado.
Some of the dead were wearing police and army uniforms, local media said.
It is thought they may have been killed in an attack by Islamist militants in the area earlier this month.
A local militant group, known as al-Shabab, has intensified attacks in recent weeks, seizing towns and raising the black jihadist flag.
It is not clear whether it has any links to the Somali group of the same name. Recently the authorities said the militants were affiliated to the Islamic State group.
In some areas, people have been hiding in the bush for days, where they say they are running out of food.