Four men were beheaded by suspected jihadists in northern Mozambique, a week after President Filipe Nyusi visited the area and pledged a "ruthless" campaign against the shadowy group.The strike happened on Saturday in Macanga, about 20km from the town of Palma and near the Tanzanian border, targeting men working in farms."Four men were killed and decapitated. One who managed to flee was shot and is under treatment. Five houses were burned. This was around 19:00 Saturday," a local resident told AFP by phone.The attackers are believed to have come from Tanzania."We are investigating this information," police spokesperson Inacio Dina told reporters on Tuesday in the capital Maputo."The attack was in a non-residential area. Our force is concentrated in the villages and the attack took place in farms," the commander of a police unit in Palma told AFP."We advise people not to circulate outside the radius protected by the security forces but because people have their crops, they insist on going out. Our forces are more in the villages to ensure the safety of homes, schools, hospitals," he said, speaking on condition of anonymity.On a visit to Palma last month, one of the districts most devastated by jihadist attacks, Nyusi vowed that security forces would be "firm and ruthless" in pursuing a group blamed for more than 30 deaths.Vast reserves of natural gas were recently discovered off the region's coast but the violence has thrown the viability of exploiting the reserves into doubt.There have been more than 10 attacks on villages in northeast Mozambique since October, featuring beheadings and arson.Thousands of soldiers and police have been deployed to Cabo Delgado to confront the wave of attacks but the violence has continued unabated.Since the first attack in October there have been reports of hundreds of arrests - as well as extra-judicial killings.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.