The UN mission in Mali said on Friday that four peacekeepers had been killed and others injured in an attack on its base in the northern town of Aguelhok.
Peacekeepers repelled the attack, carried out by "heavily armed terrorists", a UN mission statement said.
Islamist extremists are active in northern Mali.
"A provisional toll shows four peacekeepers dead and wounded. Helicopters were dispatched to the scene to evacuate the wounded," the statement said.
The UN said the peacekeepers who were killed were from Chad.
About 20 out of the estimated 100 attackers were killed in the assault, which lasted around three hours, a UN spokeswoman said.
"The attack started with mortar fire, followed by an attempted car bomb and then a direct attack."
The UN mission in Mali, known as Minusma, has deployed over 13,000 troops to contain violence by armed groups in the north and centre of the country.
It has recorded about 230 fatalities since 2013, making it the deadliest of the UN's peacekeeping missions.
Extremists linked to Al Qaeda and ISIS have stepped up activity in Africa's Sahel region in recent years, displacing thousands.
There was no immediate claim of responsibility for Friday's attack.
In a separate attack on a military post in central Mali on Friday, two Malian soldiers were killed and 10 wounded, the army said.