Mozambican militants on Saturday raided a military camp located near a site exploring a major gas field in the northern Cabo Delgado province.
It was the third such attack against a military position in the province in less than two months.
The attackers were reported to be looking for arms and food supplies.
Local media outlets say there were fierce confrontations between soldiers and the suspected Islamists, with casualties on both sides.
Some soldiers are said to have abandoned the camp to seek refuge in the nearby town of Palma.
The camp was shared by Rwandan soldiers, according to reports, although neither the Mozambican nor Rwandan army has responded to the reports.