The gunmen who kidnapped an American citizen in southern Niger issued a ransom demand Wednesday for his release, a local official said.

The hostage, Philip Walton, described as the son of a missionary living in Niger, was abducted Monday night by six men armed with Kalashnikovs on the outskirts of Massalata, a village about 10 kilometers (six miles) from the border with Nigeria.

“The kidnappers phoned the man’s father and demanded a ransom,” said Ibrahim Abba Lele, prefect of the Birni Nkonni department, which includes Massalata.

The US State Department said Tuesday it was aware of an American citizen abducted in Niger.

“We are providing their family all possible consular assistance,” it said.

Niger’s interior ministry indicated Wednesday in a statement read on national radio that the kidnappers had searched their victim’s home before fleeing “to the border area” after seizing him.

Security reinforcements have been sent to the area, and efforts with the US and Nigerian security services are underway to secure the release of the captured man, it added.

On Tuesday, a man named Bruce Walton told local radio station Niyya that his son Philip Walton had been kidnapped from his home by armed men.

“During the night six men, possibly Fulani, came on foot,” he said, referring to a nomadic ethnic group also known as Peuls.

Philip Walton had been living in Massalata with his wife and child for two years, according to his father, who himself lives in Birni Nkonni and has been in Niger for nearly 30 years.

Niger lies in the heart of the vast and impoverished Sahel, which is struggling with a jihadist insurgency that has claimed thousands of lives and driven hundreds of thousands from their homes.

Several Westerners are currently held hostage in the region.

They include American aid worker Jeffery Woodke, who was kidnapped in the central town of Abalak in October 2016 and is believed to have been taken to neighbouring Mali.

Three Europeans, including 75-year-old French charity worker Sophie Petronin, were released by their captors in Mali earlier this month under a prisoner swap arranged by the Malian government.

In August, six French aid workers and two Niger citizens were killed in the Koure wildlife reserve west of Niamey, in an attack claimed by the so-called Islamic State group.

Criminal gangs and cattle thieves often kidnap for ransom, and young Fulani herders make up many of the marauding gangs in northern Nigeria and other West African countries.

Niger also faces attacks by the Nigerian Islamist group Boko Haram on its southeastern borders.

In addition to deadly raids, Boko Haram has increasingly carried out cross-border ransom kidnappings.