Boko Haram is increasingly a regional threat and the battle against the Nigerian Islamist sect is meant to be a regional campaign -- but that's not the way it feels for Cameroon's soldiers on a desperate frontline.

"We are fed up with fighting this war all alone," a Cameroonian officer said as he described his army's resistance against Boko Haram and the lack of military support from neighbouring governments.

Nigerian Islamist extremists Boko Haram are intensifying attacks in neighboring Cameroon, targeting new villages with increasingly sophisticated weapons, as the army fears more violence in the approaching dry season.

"We're convinced that the establishment of a 'caliphate' (by Boko Haram) is aimed not only at Nigeria but also at Cameroon," Leopold Nlate Ebale, commander for an elite battalion in the border zone, told Agence France Presse.

Everyday they cross the border from Nigeria on motorbikes, donkeys or even on foot, and all are looking for safe haven from the Islamist militants of Boko Haram. 

They arrive at the already teeming refugee camp in Minawao in northern Cameroon, where they join the thousands of Nigerians who have fled the insurgency in their home country that's killed some 10,000 people.

The U.N.'s special representative for central Africa on Thursday called on increased international support in the struggle against Boko Haram, with thousands of Nigerians having fled and cross-border attacks on the rise.

"Deadly attacks by Boko Haram have gone beyond Nigeria's borders and now constitute a threat for neighbouring countries," Abdoulaye Bathily told reporters in the Gabon capital Libreville.

Islamists from Nigeria's Boko Haram killed at least three civilians in six "coordinated attacks" in the remote north of neighboring Cameroon, a defense ministry source told AFP on Tuesday.

"Six attacks were carried out almost simultaneously on Sunday," the source said on condition of anonymity, saying the fighters were pushed back across the border by Cameroonian troops.

Islamist extremist group Boko Haram has seized control of a Nigerian town near the Niger border, leading soldiers to flee and adding to its expanding reach in the region, an official said Saturday.

The insurgents were said to have taken control of Malam Fatori in Nigeria's northeastern Borno state after fighting on Wednesday and Thursday, a senior official in the Niger town of Diffa near Nigeria told Agence France-Presse on condition of anonymity.

Cameroonian troops killed 39 Boko Haram fighters in clashes with the Islamists, who were carrying out three raids on Cameroon's territory, the defense ministry said Sunday.

Friday's fighting in the far north of Cameroon near Nigeria also claimed four civilian lives, the ministry said in a statement sent to AFP.

Cameroon said Friday its army killed 107 Boko Haram fighters in ferocious combat this week in its north, in a claimed success against the Nigeria-based Islamist guerrilla group.

The "fighting of rare violence" occurred in two areas in the north on Wednesday and Thursday and also resulted in the deaths of eight soldiers, the defense ministry said in a statement read on state radio.

Cameroon's President Paul Biya on Monday vowed his government would go after the Islamist group Boko Haram "until it's totally wiped out".

He made the promise as he received 10 Chinese and 17 Cameroonians freed last week after spending months as hostages of armed men thought to belong to Boko Haram, an anti-Western rebel group in Nigeria which has been increasingly making incursions into Cameroon.

Ten Chinese and 17 local hostages have been released in Cameroon, where they were kidnapped earlier this year in raids blamed on the Nigerian Islamist group Boko Haram, Cameroon's president said Saturday.

"The 27 hostages abducted on May 16 in Waza and July 27 in Kolofata were released to the Cameroonian authorities this night," President Paul Biya said in a statement on national radio.