In February last year a gang of men with machetes ambushed two villages in western Ivory Coast, disembowelling a soldier and pulling out most of his organs before slaying three of his colleagues.
The attack marked the brutal resumption of a campaign of violence blamed on militants crossing from Liberia that has displaced thousands and claimed dozens of lives in the border area.
Experts have warned that the violence could intensify in the months ahead of presidential elections due to take place in Ivory Coast in October.
The crisis was ignited by former Ivorian president Laurent Gbagbo's refusal to accept election defeat to Alassane Ouattara in 2010, leading to a four-month conflict that claimed some 3,000 lives.
Thousands of Gbagbo's supporters fled the far west, which was hit particularly hard, across the 700-km (435-mile) border into neighboring Liberia when he was captured in April 2011.
Observers say the pro-Gbagbo political elites, now mostly in Ghana or elsewhere in west Africa, are funding incursions into western Ivory Coast by Liberian mercenaries and Ivorians recruited in Liberia's refugee camps.
The cross-border violence saw a significant spike in 2012 that saw more than 40 people killed.
In the worst incident, seven United Nations troops from Niger, 10 civilians and at least one Ivorian soldier were killed while patrolling villages south of the town of Tai.
Thirteen Liberian nationals were jailed for life but critics dismissed the trial as a witch hunt against the Krahn — the ethnicity of former president Samuel Doe who was assassinated in 1990, sparking 14 years of civil war.
Oldman James, a Liberian living in Zwedru, a provincial capital near the border, claims to have taken part in the ambush but says he has never been pursued.
'Harassed, killed and raped'
"To be frank with you there are so many reasons why we took part in these attacks," the 32-year-old, using an assumed name to protect his identity, told AFP.
"First and foremost, our brothers and sisters from the other side of the river were being harassed, killed and raped by Alassane forces. We could not sit and watch this go on."
He added that he had also been motivated by money, although he did not say who had paid him to take part.
The UN Panel of Experts on Liberia voiced concerns in November last year that Liberian refugee camps were operating as "safe havens and convenient recruiting and staging grounds for cross-border attacks".
Meanwhile British charity Conciliation Resources, which has been working in the region since 2007, said in a recent report there was "real concern" that plans for UN troop withdrawals on both sides would create a security vacuum.
The region risks a "spike in violence" ahead of the election, the charity said, describing communities on the border as living "in a persistent state of fear, especially at night, as rumors of attacks keep increasing".
An attack on Ivorian troops in January by 20 armed men which left two soldiers dead in the border town of Grabo underlined that the violence shows no sign of abating.
Accusations of the involvement of Gbagbo supporters were dismissed as "baseless" by Pascal Affi N'Guessan, the president of the former president's Ivorian Popular Front (FPI) party.
"It would surprise me if FPI leaders, who have enough problems getting by themselves, have been able to finance attacks. These comments are insulting, contrary to the philosophy of the FPI," he told AFP.
But UN investigators say Ivorian and Liberian insurgents have consistently named high-ranking members of the former Gbagbo regime as being politically or financially involved in the militant activity.
The UN views the unrest in the wider context of a regional issue arising from Liberia's two civil wars, which left thousands of former combatants jobless in the mineral-rich forests at its borders.
Many scrape a living on illegal gold mining and drugs and weapons trafficking, launching cross-border attacks to protect their own interests as much as at the behest of foreign powers.
Underlining the scope of the problem, around 50 Liberian former combatants led a series of ambushes on rangers in Sierra Leone's gold-rich Gola Forest in 2013, armed with shotguns and assault rifles.
Meanwhile violence that left at least 55 wounded in the southern Guinean city of N'Zerekore last year was blamed on former rebels who have flooded into the city from Liberia and Sierra Leone.
Peter Solo, a senior local government official in Liberia's southeastern Grand Gedeh County, describes the Ivorian border, formed mainly by the Cavalla River, as "completely porous".
He rejects evidence that attacks in Ivory Coast are being launched from across the border, however, and told AFP there had been "no direct threat from Liberia".
An officer at a border checkpoint said any solution to the unrest would have to involve Ivory Coast giving assurances to the ex-Gbagbo loyalists that they could return without fear of recriminations.
Village chiefs from both sides have been in talks but the process has been criticized by Liberian security officials for excluding border agents on the ground.
"When they get through drinking their wine and champagne, they come and ask us how the situation is," a Liberian security source told AFP.
"That is not the way to solve the problem. Those who are actively working in the field should be involved."