Bert Koenders, the UN envoy to the west African nation, said the peacekeepers were part of a patrol south of Tai in an area which the UN mission recently reinforced because of threats of attacks against the civilian population.
He condemned the Friday attack "in the strongest terms" and said the seven peacekeepers who died were from Niger.
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Kieran Dwyer, the spokesman for the UN peacekeeping department, said: "we are moving in reinforcements as soon as we have daylight."
A UN official, speaking on condition of anonymity because they were not authorised to speak publicly, said the peacekeeping patrol was attacked by a large number of people.
The official estimated that perhaps 40 peacekeepers had been in the area and were dug in overnight to protect the village against a new attack.
Koenders said in the statement that the UN mission "will take all necessary measures following this grave violation of international law."
The United Nations has had a peacekeeping mission in Ivory Coast since 2004.
At the end of April, the UN said there were about 9400 peacekeeping troops, 200 military observers and 1350 international police in the mission along with civilian staff. Over 40 countries are contributing military personnel.
