DAKAR, Senegal (AP) — The U.N. mission in Mali says four of its peacekeepers have been killed after their vehicle hit an explosive device in the central Mopti region.

Mali mission chief Mahamat Saleh Annadif said the four were killed Wednesday along the Boni-Douentza road. He said four other peacekeepers were seriously wounded and are being medically evacuated.

Annadif said six Malian soldiers were also killed in a similar manner Tuesday in the Segou region.

He said that the U.N. Mali mission is strengthening its security systems in central Mali.

The more than 11,000-strong mission in Mali has become the most dangerous in the world for U.N. peacekeepers, which are routinely attacked by Islamic militants. The threat of groups related to al-Qaida and the Islamic State group continues to spread through Mali.