Three Senegalese peacekeepers have been killed in an attack on a UN water convoy in Sudan’s troubled Darfur region.

The African Union-United Nations Mission in Darfur (UNAMID) said in a statement issued on Sunday that the attack was carried when the peacekeepers were “escorting a water convoy from the town of El Geneina to the UN mission’s regional headquarters in West Darfur.”

A fourth Senegalese soldier was also wounded in the attack.

The assault was the second deadly attack on UN peacekeepers in the region in three days.

UNAMID added that the unknown attackers hijacked a vehicle that was recovered about seven kilometers (four miles) away.

UNAMID Joint Special Representative Mohamed Ibn Chambas said the latest attack was a “grave criminal act.”

In reaction to the attack, UN Secretary-General Ban Ki-moon called on the Sudanese government to take necessary measures against the attacks.

“All too often, UNAMID peacekeepers are attacked and killed in the line of duty while helping the Sudanese bring peace to Darfur,” Ban stated.

“These attacks are unacceptable,” the UN chief added, calling on the Sudanese government to “bring those responsible to justice.”

On October 11, a Zambian military observer was killed in another attack in the city of El Fasher, North Darfur.

In July, seven Tanzanian soldiers and a Sierra Leone police officer were killed and 16 others wounded near the city of Nyala in Darfur.

Darfur has been the scene of violence since 2003, when rebels took up arms against the Sudanese government. There has also been tribal fighting in the region. More than 300,000 people have been killed in the conflict.