The militants turned a football pitch in a village into an “execution ground”, where they decapitated and chopped bodies, other reports said.
Several people were also beheaded in another village, state media reported.
The beheadings are the latest in a series of gruesome attacks that the militants have carried out in gas-rich Cabo Delgado province since 2017.
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Up to 2,000 people have been killed and about 430,000 have been left homeless in the conflict in the mainly-Muslim province.
The militants are linked to the Islamic State (IS) group, giving it a foothold in southern Africa.
The group has exploited poverty and unemployment to recruit youth in their fight to establish Islamic rule in the area.
Many locals complain that they have benefited little from the province’s ruby and gas industries.
The BBC’s Jose Tembe reports from the capital, Maputo, that the latest attack was probably the worst carried out by the militants.
Many people are shocked, and they are calling for a peaceful resolution to the conflict, he adds.
The gunmen chanted “Allahu Akbar” (“God is greatest”, in English), fired shots, and set homes alight when they raided Nanjaba village on Friday night, the state-owned Mozambique News Agency quoted survivors as saying.
Two people were beheaded in the village and several women abducted, the news agency added.
A separate group of militants carried out another brutal attack on Muatide village, where they beheaded more than 50 people, the news agency reported.
Villagers who tried to flee were caught, and taken to the local football pitch where they were beheaded and chopped to pieces in an atrocity carried out from Friday night to Sunday, privately-run Pinnancle News reported.https://emp.bbc.com/emp/SMPj/2.36.2/iframe.htmlmedia captionThe Islamic State group has been behind the growing wave of violence in northern Mozambique
Mozambique’s government has appealed for international help to curb the insurgency, saying its troops need specialised training.
In April, more than 50 people were beheaded or shot dead in an attack on a village in Cabo Delgado and earlier this month, nine people were beheaded in the same province.
Human rights groups say Mozambican security forces have also carried human rights abuses, including arbitrary arrests, torture and killings, during operations to curb the insurgency.