Congolese authorities on Saturday said they had completed a 10-week investigation and that two men will face trial.
Congolese authorities on Saturday said they had completed a 10-week investigation and that two men will face trial for the murders of American Michael Sharp and Swedish-Chilean Zaida Catalan in central Kasai province.
"That seems to have been done with quite a bit of rapidity," said UN spokesman Stephane Dujarric, adding that the Kinshasa government had yet to share the findings of its investigation with the United Nations.
Following a closed-door meeting on the murders, the UN Security Council expressed "concern about the closure of the investigation by the Congolese authorities," said Uruguay's Ambassador Elbio Rosselli, the council president.
"People who are involved may not have been properly identified," Rosselli told reporters, adding that there should be more information-sharing between Kinshasa and the United Nations to shed light on the killings.
Swedish and US investigators are also looking into the case.
A board of inquiry set up by the United Nations will present a report in late July.
France urged UN Secretary-General Antonio Guterres to set up a special investigation -- a measure that would go beyond the board of inquiry to establish the facts.
"There are still too many grey areas concerning the murder of the two experts," French Ambassador Francois Delattre told AFP, adding that the Congolese decision to wrap up the investigation was "premature."
During the closed-door session, diplomats expressed frustration with the lack of cooperation from Congolese authorities with the other investigations.
"It's been obvious in the last couple of days that more needs to be done to ensure that this is done in a proper manner," Swedish diplomat Carl Skau told reporters.
Sharp and Calatan were shot dead in March while they were investigating mass graves in Kasai. The bodies were found weeks later. Catalan had been decapitated.
In Kinshasa, the Congolese public prosecutor said earlier that he was investigating allegations that former development minister Clement Kanku may have been linked to the murders.
In a telephone conversation with an alleged militia fighter, Kanku -- now an opposition MP -- seems to be discussing setting fire to a town as well as killing officials, according to a report by The New York Times.
Kasai has seen a major spike in violence since September, when government forces killed Kamwina Nsapu, a tribal chief and militia leader who had rebelled against President Joseph Kabila.