Attackers swooped on a UN water convoy in Sudan's troubled Darfur region Sunday, killing three Senegalese peacekeepers, the United Nations said.
It was the second deadly attack on the UN mission in Darfur, UNAMID, in three days and UN leader Ban Ki-moon called on the Sudanese government to act over the incidents.
UNAMID did not identify the group behind the latest attack in which a fourth Senegalese soldier was also wounded.
The peacekeepers were escorting a water convoy from the town of El Geneina to the UN mission's regional headquarters in West Darfur when they were ambushed, UNAMID said in a statement.
The assailants hijacked a vehicle that was recovered four miles (seven kilometers) away.
Another UNAMID patrol was attacked on the same road a year ago.
UN peacekeepers have increasingly become a target for ambushes and attacks in the western region of Sudan which has been at war for the past decade. The UN says at least 300,000 people have died in the conflict.
Assailants killed a Zambian military observer with in the main North Darfur city of El Fasher on Friday.
In July, seven Tanzanian soldiers and a Sierra Leone police officer were killed and 16 others wounded near Nyala, one of the main cities in Darfur.
"All too often, UNAMID peacekeepers are attacked and killed in the line of duty while helping the Sudanese bring peace to Darfur," UN leader Ban said through a spokesman. "Theses attacks are unacceptable."
The spokesman said that Ban called on the Sudanese government "to bring those responsible to justice."
UNAMID Joint Special Representative Mohamed Ibn Chambas called the latest attack a "grave criminal act," the mission said.
He urged the Sudanese government to bring the perpetrators to justice, and thanked local authorities for pursuing the attackers and engaging them in a firefight said to have wounded people on both sides.
The Darfur war started when local groups launched an uprising in 1993 against the Arab dominated Khartoum government.
Government forces were accused of launching a brutal repression that led to war crimes and genocide charges against President Omar al-Bashir and other Sudanese officials.
Hundreds of people have died in a surge of fighting during the past year that authorities and experts largely blame on rivalry between Arab tribes acting outside government control.
UN peacekeepers have often been attacked for their vehicles and weapons.