Eight civilians died in southwestern Ivory Coast in the attack that killed seven UN peacekeepers, the United Nations said on Saturday.
"As per our information, at least eight civilians were killed, including a woman," Anouk Desgroseilliers, a spokeswoman for the UN Office for the Coordination of Humanitarian Affairs (OCHA), told AFP.
She added that Friday's simultaneous raids on several villages near the town of Tai close to the Liberian border sparked an "immediate" exodus.
"Hundreds of people have arrived in Tai, and one can imagine that thousands of others are on the road," she said. "Thirty-five families have crossed the border" into Liberia, she added.
The UN peacekeepers from Niger killed in an ambush on Friday had been patrolling in an area between two villages after hearing rumours of an imminent attack on communities in the region.
Ivory Coast's west, by far the most unstable part of the country, has been plagued by deadly attacks since a political and military crisis that started at the end of 2010 and left some 3,000 people dead throughout the country.
It was the biggest loss suffered by the 10,000-strong UN peacekeeping mission in Ivory Coast since it was first deployed in 2004 in the country divided following an unsuccessful coup against then president Laurent Gbagbo.
Desgroseilliers said aid workers from the International Committee of the Red Cross, the Danish Refugee Council and local groups were on site to assist those displaced, including supplying food and water.
OCHA was trying to coordinate the response to the situation with local authorities, she added.
The UN Security Council "condemned in the strongest terms" the deadly ambush and called on the Ivory Coast government to "work with all relevant parties to identify and bring the perpetrators to justice."
UN leader Ban Ki-moon said he was "outraged" by the killings of the peacekeepers and warned that more UN troops "are still in danger."
"Even tonight, after the attack, more than 40 peacekeepers remain with the villagers in this remote region to protect them from this armed group," the UN chief said. "My thoughts are with these brave peacekeepers and the community they are protecting."
The UN denounces the "very serious violation of international law", a spokesman for the UN Operation in Ivory Coast (UNOCI) added.
The country's deputy defence minister Paul Koffi Koffi said the attackers had crossed over from neighbouring Liberia, adding that two Ivorian soldiers and at least one civilian may also have been killed.
"There's panic in the villages, many are fleeing into the forest, others are heading for Liberia," a resident of Para village told AFP by phone.
In a report published on Wednesday, Human Rights Watch said at least 40 people had been killed since July 2011 in raids the group blamed on fighters loyal to Gbagbo.
Gbagbo refused to stand down after elections in 2010 that handed victory to his rival Alassane Ouattara. He was captured on April 11, 2011, after a period of fighting between the two sides.
The former president has been in custody in The Hague since November awaiting trial by the International Criminal Court on charges of crimes against humanity.