Yaounde: In the villages that line the border with Nigeria, even those charged with protecting Cameroonians from Boko Haram fighters fear the fall of darkness.
"When night falls, we tremble. We don't sleep," said a Cameroonian policeman from a far-northern border town, on condition of anonymity.
The Nigeria-born Islamist group has stepped up raids into northern Cameroon in recent days, murdering and stealing with impunity despite military efforts to clamp down on their bloody insurgency.
On Sunday local police said one of their officers was killed during an attack on the village of Nariki, 500 metres from Boko Haram's Nigerian stronghold of Tarmoa, adding to scores of deaths from raids on local towns this month.
The militants have long used Cameroon to launch attacks on Nigeria as the border between them is extremely porous, with no buffer-zone clearly separating the two countries.
Earlier this month they stole a pick-up truck and weapons in a raid on a police post in Bomberi, Cameroon, only to abandon it on Nigerian territory where it was found by troops days later, said another Cameroon police officer.
Weapons and goods cross the border freely too: the remote northern Cameroon town of Amchide has become a hotbed for Boko Haram fighters and a hub for trafficking to finance their recruitment.
Cameroon, like other west African countries, has beefed up its operations against Boko Haram since the kidnapping of more than 200 Nigerian schoolgirls three months ago sparked an international outcry.
The army claims to have killed many militants in recent weeks and suspected members and collaborators have been arrested and sent to the capital, Yaounde.
Cameroon's elite Rapid Intervention Battalion (BIR) recently destroyed one Boko Haram camp during a foray across the border into Tarmoa, said the second officer.
Supported by international governments, they have also targeted the Sambisa forest near the shared border where Nigerian authorities believe the kidnapped schoolgirls may still be hidden in the militants' camps.
- Constant threat -
But Cameroon's efforts have done little to stem Boko Haram's bloody five-year insurgency or stop almost daily attacks that have left local communities living in constant fear.
"Boko Haram is disorganised because of joint operations by the Cameroonian and Nigerian armed forces, but its activists carry out attacks here and there in Cameroon," the second officer said.
The first policeman said the insurgents can easily escape as "they know very well" where the Cameroonian troops are located.
The Islamist group, blamed for slaughtering more than 2,000 civilians already this year, has increasingly targeted remote border communities, razing entire villages.
Two Cameroonian shepherds were killed and 200 cattle stolen by militants on July 10 during a raid in the village of Bame, less than 10 kilometres (six miles) from the Nigerian border, said the first police officer.
And suspected Boko Haram fighters kidnapped a 20-year-old Cameroonian earlier this month from the village of Balgaram after an attack was foiled by the army.
Senior local figures are also being intimidated to stop them from helping the government against Boko Haram.
In Limani, which lies in the flashpoint zone between Nigeria's Tarmoa and Amchide in Cameroon, militants kidnapped the sons of a traditional chief who has been a go-between for the group.
"They were intimidating the father," said the second police officer. "He's a go-between for Boko Haram, which suspects him of collaborating with Cameroonian forces."
A lack of coordination by military forces -- particularly between Nigeria and Cameroon -- has hampered the efforts to stop the insurgents.
That was made clear during a botched attempt to rescue 10 Chinese road workers who were kidnapped in May.
A negotiator was hurt when a team of Cameroonians sent to bring back the workers in early July was fired on by the Nigerian army, which was unaware of their operation, said the second officer.
"There is currently a tacit agreement between Nigeria and Cameroon to let soldiers from both countries cross the border either way during actions against Boko Haram," he added.
But officially, the Yaounde government does not allow any right of pursuit by Nigerian forces on its territory.