Fighters who backed former Ivory Coast president Laurent Gbagbo have infiltrated refugee camps in Ghana and are accused of attacking security bases back in Ivory Coast, according to Ivorian officials.

Human rights groups say the presence of Gbagbo's ex-fighters in the camps poses a threat to the security of refugees.

Some fighters had been allowed to slip into the three refugee camps housing Ivorians, said Tetteh Padi, program coordinator of Ghana's Refugee Board. In one example, Ghanaian authorities in May lost track of nearly 150 suspected fighters who were supposed to be transferred to a maximum security prison and now their whereabouts are unknown.

"We have known for a fact that some of them have infiltrated the camps," said Padi. "Some of them have friends, relatives in the camps. So they have gone in there unofficially."

Ghana's failure to monitor the ex-combatants is very worrying, said Matt Wells, West Africa researcher at Human Rights Watch.

"Ghanaian authorities appear to have dropped the ball in losing track of many Ivorian ex-combatants, putting civilians in refugee camps at risk of sexual violence and child recruitment, among other protection concerns," Wells said.

Ivorian President Alassane Ouattara's government alleges that Gbagbo fighters in the camps have taken part in recent attacks on military positions in Ivory Coast. Since early August, about 10 such attacks have been carried out throughout the country, with some allegedly perpetrated by fighters based in Liberia as well as Ghana.

One attack on a town at the border between Ivory Coast and Ghana in September prompted Ivory Coast to close its land and sea frontiers with Ghana for more than two weeks.

However, Padi said accusations that fighters in refugee camps had been involved in the attacks are baseless.

"They're totally false in our opinion because we know everything that goes on in the camps," he said.

Ampain, the largest of the three refugee camps for Ivorians in Ghana, is a sprawling, unfenced facility now home to some 4,000 people.

Ghanaian authorities refused to allow The Associated Press to visit the refugee camp and deleted photos taken by a reporter who interviewed Ivorians living there.

Patricia Ange Oulai, a 29-year-old refugee in the camp, said the presence of the fighters had her worried for her safety. "I regret that they are here because with everything happening people think they are the ones that are going to do the coup" back in Ivory Coast, she said.

Post-election violence erupted in Ivory Coast after Gbagbo refused to cede office despite losing the November 2010 runoff vote to Ouattara.

Gbagbo was arrested in April 2011 and later transferred to the International Criminal Court at The Hague where he faces charges of crimes against humanity. High-level Gbagbo loyalists have sought asylum in Ghana and other West African countries.

A report from a United Nations panel of experts presented to the Security Council last month alleges that these allies have worked to destabilize Ivory Coast from their base in Ghana.

On Oct. 13, Ghanaian security forces conducted their first roundup of ex-combatants at Ampain. Padi, the program coordinator for the Ghana Refugee Board, said 43 suspected ex-combatants were detained in the early morning raid, though some were released after authorities concluded they were not fighters.

Padi said the raid was prompted in part by allegations from the Ivorian government that Ghana has been used as a staging ground for the recent attacks.

"The idea is to make sure we know what they are up to so that we will not get accusations coming from Ivory Coast that we are harboring ex-combatants who are attacking Ivory Coast," he said.

The refugee camps should be completely cleared of ex-combatants so as to maintain their civilian character, said Andrea Lari, director of programs for Refugees International.

"I think that it is urgent to address these allegations and delaying the intervention is only going to make matters worse," Lari said.

There are no good figures on the number of ex-combatants who fled into Ghana both during and after the post-election conflict, though most estimates run well into the hundreds. Veton Orana, protection officer for the U.N. refugee agency, said authorities began noticing an influx of potential fighters at the Elubo border crossing after the fall of Gbagbo in April 2011.

Orana said some ex-combatants may have been able to conceal their status when they crossed at Elubo, and that others may have entered Ghana at other places.

David Dalli, a 33-year-old former soldier in Gbagbo's army who now lives at Ampain, said it was easy to pass as a civilian when he crossed into Ghana.

"When I came here, I just said I was a civilian to hide who I was," said Dalli, who took part in fighting in Abidjan.

Paul Koffi Koffi, Ivory Coast's deputy defense minister, said by phone from Abidjan that the Ouattara government was not happy that ex-combatants had found their way into the refugee camps.

"The attackers at the different towns and the different army positions are coming from Ghana and are also coming from the refugee camps in Ghana," he said. "Even if they are in some refugee camps, they have freedom of movement, so some are coming here and then going back to Ghana. And we don't know what they are doing."