ABIDJAN, Ivory Coast – Masked gunmen with rocket launchers are blocking access to what officials believe may be a mass grave site in Ivory Coast, the United Nations said, as concerns grow that the West African nation that suffered a 2002-2003 civil war could return to conflict.

The U.N. reported that heavily armed forces allied with Laurent Gbagbo and joined by masked men, were preventing people from getting to the village of N’Dotre, where the U.N. said “allegations point to the existence of a mass grave.”

The U.N. did not elaborate on the possible victims, though it has expressed concerns about hundreds of arrests, and dozens of cases of torture and disappearance during the political turmoil since the presidential runoff vote was held nearly a month ago.

“The number of dead, wounded and missing persons is increasing rapidly,” U.N. deputy spokesman Farhan Haq said late Thursday.

Alain Toussaint, an adviser for Gbagbo, has said that he didn’t believe soldiers or people close to Gbagbo would carry out such acts of violence .

Gbagbo has refused to step down from the presidency despite international calls for his ouster. The international community recognizes Alassane Ouattara as the winner.