Chad will send a large number of troops to neighbouring Cameroon to help it fight increasing incursions from Boko Haram Islamist militants attacking from Nigeria, the Central African nation's President said on Thursday.

The announcement by President Paul Biya did not specify how many troops Chad will send, but comes a day after the Chadian government said it will actively help Cameroon fight Boko Haram militants.

Chad President Idriss Deby Itno "has decided to send a large contingent of Chadian armed forces to help the Cameroonian Armed Forces facing...repeated attacks from the Boko Haram terrorist sect," Mr. Biya said in the statement on the presidency's website.

Mr. Biya has called for international military help to fight the Islamist militant group that has seized swathes of northern Nigeria and is threatening neighbours who share borders with the northeastern zones occupied by the group.

Boko Haram, which aims to carve out an Islamist state in northern Nigeria, has stepped up attacks in the region as Nigeria, Africa's biggest economy, prepares for a crucial Feb. 14 presidential election.

The group has also carried out a number of attacks and raids across the border in northern Cameroon, prompting the government to deploy thousands of troops including special forces.

United Nations Special Representative for West Africa Mohamed Ibn Chambas on Thursday, urged Nigeria, Cameroon, Chad and Niger, the four nations in the region immediately threatened by Boko Haram, to set aside their differences and agree on a command structure and strategy for a regional force to defeat the militants.