Ten people were beheaded in a village in northern Mozambique, police said on Tuesday, as local sources blamed the attack on Islamists.
The predawn attack on Sunday occurred in two small villages close to the border with Tanzania and not far from Palma, a small town gearing up to be the country's new natural gas hub in the northern province of Cabo Delgado.
"There are 10 citizens who have been hideously killed," Inacio Dina, the national police spokesman, told a news conference in Maputo, adding that the attackers used machetes.
Two of those killed were 15- and 16-year-old boys, who had set out in the early hours "hunting mice to eat," said the police. Villagers earlier had said the fatalities included children.
No arrests have been made yet.
Without naming the group of attackers, police's Dina vowed that "we will hunt and find them and take them to the court as happened with others," in apparent reference to attacks that occurred elsewhere in the same province in October.
Police reinforcements have been sent to the villages to step up security.
"The environment is scary," Dina said.
Cabo Delgado province has seen a number of attacks by suspected radical Islamists since October.
In the latest attack, one victim was the leader of Monjane village, a local resident said, withholding his name for fear of reprisals.
"They targeted the chief as he had been providing information to the police about the location of al-Shabab in the forests," he told AFP, referring to an armed group believed responsible for a deadly October attack on a police station and military post in the town of Mocimboa da Praia.
Two officers died and 14 attackers were killed then in what was believed to be the first jihadist attack on the country.
The group has no known link to the Somali jihadist group of the same name.
In the following weeks, at least 300 Muslims, including Tanzanians, were arrested and several mosques were forced to close.
Alex Vines, a specialist analyst on Mozambique for the London-based independent policy group Chatham House, told AFP that the "new attacks are unsurprising and a reminder of the seriousness of the situation."
"A number of independent assessments of the situation in Cabo Delgado, conducted over the last three months, have concluded that the security situation [there] remains fragile and continued attacks probable," he said.
Police suspect the attackers are hiding in the forests surrounding the villages. A local villager said police were called during the attack but "arrived very late and the attackers were already gone. Nothing was stolen."
"They are becoming much more radical now as they are facing attacks from government," said another villager.
"This attack is a worrying sign of the deterioration of the situation," said Eric Morier-Genoud, a lecturer in African history at the Queen's University Belfast. "On the one hand, the rate of attacks appears to intensify. On the other hand, the methods seem to be radicalized, with decapitations becoming more and more common."
A study published last week by Mozambican academic Joao Pereira said up to 40 members of the radical group "have been trained by movements" that operate in the Great Lakes region of the Democratic Republic of Congo, Somalia and Kenya.
The increase in attacks in the country's north could present a problem for Mozambique, which holds general elections next year and has its eyes set on recently discovered gas reserves.
Vast gas deposits discovered off the shores of Palma could transform the impoverished country's economy.
Experts predict that Mozambique could become the world's third-largest exporter of liquefied natural gas (LNG).
But Morier-Genoud suggested the group won't pose immediate "significant danger" to the gas project, urging that government engages the northern region from social and religious platforms instead of resorting strictly to a military response.
The country's north has largely been excluded from the economic growth of the last 20 years, and the region sees itself as a neglected outpost, giving the radical al-Shabab-style ideology a receptive audience.
Mozambique this month passed an anti-terrorism law that punishes terrorism activity with more than 40 years in jail.