An al Qaeda offshoot in North Africa has claimed responsibility for an attack Monday in northern Mali on an International Red Cross vehicle that killed one aid worker and left one injured.

The Movement for Oneness and Jihad in West Africa (MUJAO), a splinter group of al Qaeda in the Islamic Maghreb (AQIM), said its fighters were behind deadly attack.

The gunmen opened fire on the truck around 11am Monday as it traveled from the northern city of Gao to Niamey, the capital of neighboring Niger, to pick up equipment for a medical facility in Gao. Malian Red Cross spokesman Valery Mbaoh Nana told VICE News the vehicle was "clearly marked with the Red Cross emblem."

"It is hard to imagine that this attack will be without consequence for the people who enjoy free healthcare at the hospital in Gao," Mbaoh Nana said, noting that the Red Cross has provided the facility with "logistical and human resources since 2012."

Mbaoh Nana said the Red Cross has suspended all travel in the region until further notice.

International Committee of the Red Cross (ICRC) spokeswoman Claire Kaplan told VICE News that the aid worker killed in the attack was a 38-year-old Malian employee of the Red Cross, and that his wounded colleague is also from Mali.

An African military source with MINUSMA, the UN peacekeeping mission in Mali, told France 24 that the ambush was "carefully planned," and "carried out by at least six terrorists."

"With the help of the hand of Allah, we killed near Gao, in Muslim territory, a driver who worked for the enemy," MUJAO spokesman Abou Walid Sahraoui told AFP, adding that the group had "achieved what we wanted with this attack."

MUJAO formed in 2011 and took control of Gao, northern Mali's largest city, the following year. The militants also occupied and shared control of several surrounding towns with other insurgent groups.

In January 2013, an unprecedented attack by Islamist forces on the south of the country triggered Operation Serval, a French military intervention that halted the jihadist advance and helped the Malian government regain control of Gao.

The UN launched MINUSMA after Operation Serval ended in July 2014. France redeployed its troops as part of Operation Barkhane, an anti-Islamist military campaign spread across Africa's Sahel region.

Alain Antil, a researcher at the French Institute for International Relations and an expert on the region, told VICE News that the French military operations have failed to "neutralize" MUJAO and other militant groups, and that reports from the region suggest they are now slowly "regaining their strength."

"These groups are in no state to control entire regions like they did in 2012," Antil said, "but they can still carry out attacks."

According to Antil, there aren't enough UN peacekeepers and French troops on the ground to secure a region as large as northern Mali.

"Operation Barkhane and the MINUSMA deploy 10,000 men across a territory that is bigger than metropolitan France," Antil said. "When you consider how important an axis the road from Gao to Niamey is, you can see how fragile the system is."

Mbaoh Nana, the Red Cross spokesman, said the organization is "aware of the threat" that comes with operating in northern Mali and will typically "alert key players in the region to our movements, so that all the forces present in the region are aware that the Red Cross is on the ground."

He couldn't understand why militants would choose to target aid workers.

"We have had a steady presence here for a long time," Mbaoh Nana said. "Even back in 2012. We were one of the only humanitarian organizations still present."

Follow Matthieu Jublin on Twitter @MatthieuJublin