Two Spanish journalists and an Irish citizen were killed in an armed ambush on an anti-poaching patrol near a nature reserve in eastern Burkina Faso, the Burkinabe and Spanish authorities said on Tuesday. The three foreigners and a member of the Burkinabe armed forces went missing on Monday after a morning attack on a convoy of security forces, forest rangers and expatriates, according to Burkina Faso"s government. Spain"s Prime Minister Pedro Sanchez said the two journalists - David Beriain and Roberto Fraile - had been filming a documentary before they were killed. "The worst of news is confirmed," Sanchez posted on Twitter. Ireland"s foreign ministry said it had been in contact with the family of the Irish citizen as well as with European Union and Spanish colleagues. "The situation is complex and officials are working with relevant actors on the ground," it said, without commenting further. Spanish media producer Movistar+ paid tribute to those killed including Beriain, who had worked on a number of documentaries for the company. It named the Irish citizen as Zambian-born Rory Young, head of anti-poaching organisation Chengeta Wildlife. The Burkinabe government reported an increase in violence elsewhere in the past 72 hours, with around 10 civilians killed in a spate of armed raids on villages. Burkina Faso, like much of West Africa"s Sahel region, faces a deepening security crisis as groups with links to al Qaeda and Islamic State step up attacks on the army and civilians despite the presence of French and U.N. forces. No one has yet claimed responsibility for the ambush on the anti-poaching patrol, which took place on a road to the vast forested reserve of Pama. The government said it had not identified the assailants, whom it described as "terrorists". Abundant vegetation and the poor condition of the backcountry roads would have made it easy for the assailants to take the convoy by surprise, said Burkinabe police superintendent and security expert Rachid Palenfo. "It happened where the road is deteriorated, it means that you can"t drive fast," he said. The unit that was ambushed was part of a new joint army, police and forestry unit that had just gone through six months of training and was starting operations in conservation areas around Pama on the border with Benin and Togo. The region"s worsening security has led to one of the world"s most acute humanitarian crises, U.N. agencies said on Tuesday. Twenty-nine million Sahelians - an all-time high - are in need of aid and protection, 5 million more than last year, they said.