At least 29 soldiers have been killed in an attack in western Niger, according to the country’s defence ministry.

A three-day national mourning period was declared in the country on Tuesday over the incident that involved “improvised explosive devices and kamikaze vehicles by more than a hundred terrorists”, according to a televised statement made by the ministry on Monday night.

It added that two soldiers were seriously wounded and “several dozen terrorists” were also killed.

The attack took place near the country’s border with Mali during military operations aimed at “neutralising the threat posed” by the ISIL (ISIS) armed group in the area, according to the ministry.

“Communications from the terrorists, who were forced to withdraw, have been intercepted,” the statement said, adding that the attackers “benefitted from outside expertise”, without giving any further details.

Attacks by armed groups have plagued Africa’s Sahel region for more than 10 years, breaking out in northern Mali in 2012 before spreading to neighbouring Niger and Burkina Faso in 2015.

The “three borders” area between Niger, Mali and Burkina Faso is regularly the scene of attacks by fighters affiliated with ISIL and al-Qaeda.

The violence has fuelled military takeovers in all three countries, with Niger the latest to fall to a coup on July 26 that overthrew Mohamed Bazoum, its democratically elected president.

The latest violence comes as the country’s coup leaders indicated they were considering neighbouring Algeria’s offer to mediate talks for a transition back to civilian rule.