Eight civilians died in Ivory Coast in raids near the Liberian border that also killed seven UN peacekeepers and sparked an exodus of thousands from the area, the United Nations said on Saturday.

The UN Security Council has meanwhile "condemned in the strongest terms" the deadly attack and called on the Ivory Coast government to "work with all relevant parties to identify and bring the perpetrators to justice".

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 started in late 2010, leaving some 3,000 people dead throughout the country.

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.

UN Office for the Coordination of Humanitarian Affairs (OCHA) spokeswoman Anouk Desgroseilliers told AFP that in the latest violence, "as per our information, at least eight civilians were killed, including a woman".

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 to seek safety there, she added.

Ivory Coast's deputy defence minister Paul Koffi Koffi said the attackers had crossed over from Liberia, adding that two Ivorian soldiers and at least one civilian may also have been killed.

"We are shocked by this unacceptable act," Niger Justice Minister and government spokesman Marou Amadou told AFP on Saturday. "All measures should be taken to see that this serious act does not go unpunished."

But the 900-strong Niger contingent "will continue to work with ONUCI", the UN mission in Ivory Coast, he said.

Friday's attack brought the biggest loss suffered by the 10,000-strong UN peacekeeping mission in Ivory Coast since it was deployed in 2004 in the country divided after a failed 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, the spokeswoman added.

"It's real panic here... people are taking little bundles and fleeing on foot," Tai's mayor Desire Gnonkonte told AFP over the telephone.

"We are scared," said Tai womens' affairs official Madeleine Tagnon. "Why do militias cross the border every time to come and kill us?"

Ange Joelle, who crossed over to the eastern Liberian village of Glaro Ubor, said: "I walked through the bush with my child on my back. I don't know where the rest of the family is."

UN leader Ban Ki-moon said he was "outraged" by the killings 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 UNOCI said.

"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 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.