* Suspects arrested in Liberia
* Ivory Coast expects them to be extradited
By Carolyn Cohn
LONDON, July 27 (Reuters) - Four men have been arrested in connection with the ambush killings in Ivory Coast of seven U.N. peacekeepers on its border with Liberia, Ivory Coast President Alassane Ouattara said on Friday.
An adviser to Ouattara said the four had been arrested in Liberia and would be extradited to Ivory Coast to stand trial.
The seven United Nations peacekeepers, all from Niger, were killed on June 8 when their patrol came under fire near the town of Tai, close to the porous border, in what Ivorian authorities said was a cross-border raid.
"We have just arrested four people who perpetrated that attack and killed the seven peacekeepers," President Alassane Ouattara said during a visit to London, where he was planning to watch the Olympics opening ceremony.
He said those arrested included "the head of the operation", but gave no further information as to the identities or nationalities of the four men.
Liberian government officials said they were not immediately able to comment on Ouattara's remarks while Ivory Coast's U.N. mission, UNOCI, said it was not aware of any arrests.
A decade of north-south partition and simmering political crisis in the world's top cocoa grower ended last year with a brief but brutal civil war that erupted after former President Laurent Gbagbo refused to acknowledge defeat in 2010 polls.
Around 3,000 died before Gbagbo was captured by troops loyal to Ouattara, who were backed by French and U.N. forces. Gbagbo is in The Hague awaiting trial before the International Criminal Court accused of war crimes and crimes against humanity.
Chanting supporters and opponents of Ouattara gathered outside the venue where he spoke but were kept apart by police barriers.
Ouattara said a national commission of enquiry had completed an investigation on July 18 into crimes committed by the two warring factions during the conflict, but said he had not yet seen its findings.
"When the battle started you had atrocities committed, probably by both sides," he said. "But this needs an enquiry, that's why we set up the National Enquiry Commission...when I go back I will have the report."
The U.N. Security Council renewed UNOCI's mandate on Thursday, reducing its military force by one battalion, or around 700 to 1,000 soldiers, to just under 9,000 troops. (Additional reporting by Alistair Smout, Joe Bavier in Abidjan, and Alphonso Toweh in Monrovia; Editing by Michael Roddy)