Four Moroccan truck drivers went missing on Saturday as they crossed the restive border area between Burkina Faso and Niger, according to a source from the Moroccan embassy in Burkina Faso and a Moroccan transport union.

Three trucks, one carrying a spare driver, disappeared as they drove without an escort from Dori in Burkina Faso to Tera in Niger, an area known for Jihadist threats, the diplomatic source said.

Junta-led Burkina Faso and Niger are battling Islamist militant groups linked to al Qaeda and Islamic State, whose insurgencies have destabilised Sahel states in West Africa over the past decade.

The Moroccan diplomatic source said the embassy was working together with Burkina Faso authorities to find the drivers.

Authorities in Burkina Faso have been organising security convoys to escort trucks in the border area to protect against militant attacks, the source said.

The trucks set off after waiting for a week without getting an escort, Echarki El Hachmi, Secretary General of Morocco's transporters' union, told Reuters.

The trucks, loaded with infrastructure equipment, departed weeks ago from Casablanca heading to Niger, he said.

El Hachmi urged more protection in areas of high risk as the number of Moroccan trucks crossing the Sahel continues to rise.

Earlier this month, a convoy of Moroccan trucks was attacked on the Malian border with Mauritania, although there were no casualties, El Hachmi said.