DAKAR, Senegal (AP) — A United Nations children's agency staffer and five other education workers have been killed in an attack in Central African Republic, the U.N. agency said Wednesday.

The team came under attack Sunday while traveling near Markounda, a remote northwestern area near the border with Chad where more than 7,000 people have sought refuge in recent months, UNICEF said. The team had planned to train community teachers for 2,000 children affected by the country's ongoing violence among armed groups.

All the victims were Central African nationals, including two officials with the education ministry.

"We are shocked beyond words by this brutal and senseless attack on people who have dedicated their lives to helping others," said Christine Muhigana, UNICEF's country representative.

Central African Republic has faced deadly interreligious and intercommunal fighting since 2013, when predominantly Muslim Seleka rebels seized power in the capital, Bangui. Mostly Christian anti-Balaka militias fought back, resulting in thousands of people killed and hundreds of thousands displaced.

The impoverished country saw a period of relative peace in late 2015 and 2016 but violence has intensified and spread in the past year.

In August, clashes between a militia and a self-defense group in the southeast killed 30 civilians, including six Red Cross volunteers.

The violence has blocked many humanitarian workers from doing their work.