The Cameroonian army says five of its soldiers have been killed in clashes with Islamic extremist group Boko Haram in the country's far north, which also left 86 of the militants dead.

The "series of clashes" took place on Monday in the Waza region near the border with Nigeria, said Colonel Didier Badjeck, a spokesman for the Cameroonian defence ministry.

He said the Cameroonian army had recovered one armoured vehicle from Boko Haram and damaged another.

The troops who were killed belonged to Cameroon's elite Rapid Intervention Battalion (BIR), which is on the front line in the fight against Boko Haram.

A Cameroonian soldier speaking on condition of anonymity said, "an ambush by Boko Haram" led to nearly three hours of gun battles.

More than 2,000 Cameroonian soldiers have been deployed in Cameroon's far north region since August last year.

An army official announced on Monday that more than 1,000 people suspected of being affiliated with Boko Haram were being held in the town of Maroua, also in the far north of the country.

"At the moment, the prison of Maroua is holding more than 1,000 Boko Haram [suspects]," said Colonel Joseph Nouma, commander of a local operation to combat the Islamist militants.

Boko Haram has grown in power in the area, where Cameroon and Nigeria are linked by a bridge.

Militants have carried out repeated massacres of civilians and attacks on villages there, but are now increasingly active against military targets.

The Sunni jihadist group has killed and kidnapped thousands as part of its bid to create an Islamic state in northern Nigeria.

African leaders pledge $87m to fight Boko Haram Meanwhile, more than 160 people suspected of having links to the militant group have been arrested in Niger, a police spokesman said on Monday.

The West African country has experienced a surge in violence from the group, whose heartland lies on the other side of Niger's southern border.

Last week, thousands of residents fled the border town of Diffa following a series of raids and suicide bombings.

Boko Haram has stepped up attacks on neighbouring countries in the Lake Chad region, prompting an international offensive against them.

Cameroon has joined a military alliance with Chad, Niger and Nigeria to battle the five-year insurgency waged by Boko Haram.

At a summit in Cameroon on Monday, the presidents of the 10-nation Economic Community of Central African States (CEEAC) pledged to set aside $110 million to combat the Islamist militants.

"My counterparts from the CEEAC and I decided to create an emergency fund of 50 billion CFA francs ($110 million) to fight Boko Haram," Gabon's president Ali Bongo said on his personal Twitter account.