Cameroonian troops fought "heavy clashes" Tuesday with Boko Haram militants near the border with Nigeria as a security summit kicked off in Niger on a regional plan to stop the Islamist fighters. 

Boko Haram insurgents from neighboring Nigeria attacked the far northern Cameroon border village of Bonderi, a source told AFP, adding that "it's too early to give a casualty toll".

Boko Haram freed two dozen hostages after a mass abduction by its militants in Cameroon, as Chad prepared Monday to engage in the international battle against the extremist group.

Twenty-four of the 80 people taken hostage by Boko Haram in the north of Cameroon Sunday were released as Cameroonian armed forces pursued the Islamist extremists, according to a government source.

Boko Haram fighters from Nigeria on Sunday kidnapped at least 60 people in a new attack in northern Cameroon in which some people were killed, police said.

The Islamist militants "burst into two villages in the Tourou area... They torched houses and left with around 60 people. Most of them were women and children," a police officer told Agence France-Presse.

Tens of thousands of people rallied in the capital of Chad on Saturday in support of the authorities' decision to send troops to fight Nigeria's Boko Haram Islamists.

Prime Minister Kalzeube Pahimi Deubet led the demonstrators as they marched from city hall in the capital N'Djamena to the Place de Nation square, carrying Chadian flags and chanting in French and Arabic: "Kick the forces of evil out of our territory."

Cameroon's President Paul Biya announced Thursday that Chad will send troops to aid his country's army fight Boko Haram militants from Nigeria, a government spokesman said.

"Chadian President Idriss Deby Itno has decided to send a substantial contingent of Chadian troops to back the Cameroonian armed forces who have faced repeated attacks from the Boko Haram terrorist sect with courage, determination and vigilance," the Cameroonian spokesman said in a statement.

Nigerian Boko Haram Islamists launched an attack Monday on a military base in northwest Cameroon, forcing many to flee the area, the official sources said.

"As soon as people heard the first gunfire they fled the city" of Kolofata, a local Cameroonian source told AFP.

A Nigerian archbishop called Monday for the same international support to tackle Boko Haram as France has received since it was hit by Islamist attacks last week.

"I see the very positive response of the French government tackling this issue of religious violence after the killing of their citizens," said the Roman Catholic Archbishop of Jos in central Nigeria, Ignatius Kaigama.

Boko Haram leader Abubakar Shekau has threatened Cameroon in a video message on YouTube, warning that the same fate would befall the country as neighboring Nigeria.

The video, which was posted on January 5, is directly addressed to Cameroon's President Paul Biya after repeated fighting between militants and troops in the country's far north.

Cameroon has sent warplanes into action against Nigerian Boko Haram fighters for the first time, after the large force of jihadists crossed the border and seized a military camp, the government said.

Cameroon's army said Thursday its troops had killed 116 Nigerian fighters from the Islamist Boko Haram group in the far north.

Insurgents attacked an army base in Amchide on the border with Nigeria on Wednesday, but soldiers repelled them, inflicting heavy losses, the defence ministry said.