Maputo (AFP) - A shadowy Islamist group that has terrorised northern Mozambique killed 52 villagers on April 7 after locals refused to be recruited to their ranks, according to police cited by local media Tuesday.

"Recently, the criminals tried to recruit young people to join their ranks, but there was resistance on the part of the youths. This provoked the anger of the criminals, who indiscriminately killed -- cruelly and diabolically -- 52 young people," police spokesman Orlando Mudumane told the state-owned broadcasting service.

The killings took place in the village of Xitaxi in of Muidumbe district.

Mudumane said the villagers were "massacred", either shot dead or beheaded.

Police said they have launched a manhunt for the attackers to bring them to justice.

Militants have in recent weeks stepped up attacks as part of a campaign to establish an Islamist caliphate in the gas-rich region, seizing government buildings, blocking roads and briefly hoisting their black-and-white jihadist flag over towns and villages across Cabo Delgado province.

For more than two years the jihadists mainly targeted isolated villages, killing more than 900 people, according to the Armed Conflict Location & Event Data Project (ACLED).

The unrest has forced hundreds of thousands of locals to flee and raised concern among energy giants operating in the gas-rich region.

More than 200,000, according to a local Catholic archbishop, Dom Luiz Fernando, have escaped.

Some have sought refuge among friends and relatives in the port city of Pemba, the capital of Cabo Delgado.

Islamic State Central Africa Province (ISCAP), affiliated with the Islamic State group, has claimed some of the attacks in the region since last year.

Since October 2017, when they first staged an attack in the province, the group hid their identities, but in recent weeks, it has unmasked its fighters and openly declaring its goal of turning the gas-rich region into a caliphate

"We don't want a government from unbelievers, we want a government from Allah," the group member added, speaking in the local Kimwani language to residents rounded up for a rally.

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The fighters have since emerged from their hideouts and openly taken control of three Cabo Delgado districts.

Locally they are known as Al-Shabaab, although they have no known links to the ruthless jihadist group of that name operating in Somalia.

It was on the same day April 7 in Muidumbe, that local sources told AFP that the militants went on a rampage burning bridge construction equipment, and ransacking schools, hospitals and a bank.

Before the raid, the attackers used loudhailers to warn villagers "not to run away but stay inside the house," the source said.

In the same district the militants recorded a video of themselves addressing locals in the region's local vernacular of Kimwani and Swahili.

Military troops and special police units deployed to Cabo Delgado have failed to rein in the insurgency.

Last week, police chief Bernardino Rafael downplayed the attacks, but conceded that there had been "criminal incursions".