N'DJAMENA (Reuters) - Military chiefs from the Lake Chad region have finalised details of the deployment of a joint force to fight Nigerian Islamist group Boko Haram, designating three command posts in Nigeria and Cameroon, military sources said on Saturday.

At a two-day meeting in N'Djamena, which concluded late on Friday, military commanders from Nigeria, Chad, Niger, Cameroon and Benin agreed to accelerate the deployment of the 8,700-strong force, which will have its overall command center in the Chadian capital.

A disjointed campaign by Nigeria, Chad and Niger swept Boko Haram out of the towns of northeast Nigeria earlier this year but the group, which has sworn allegiance to Islamic State, has killed hundreds of people in the last three months in those three countries, as well as neighboring Cameroon.

Regional governments have since dragged their heels in establishing the integrated taskforce, supposed to start operations on July 31.

"We have finalised the details of the deployment of troops," said one officer who took part in the meeting. "The force commanders will inspect the sites of the barracks in the coming days."

The military sources said the two command posts for the joint force in Nigeria would be in Baga, on the shores of Lake Chad, and in Gambaru, on the border with Cameroon.

The third command post would be established further south in the Cameroonian town of Mora, on the other side of the border from the Nigerian settlement of Gwoza, where Boko Haram formerly had its headquarters.

The chiefs of staff also ordered officers seconded to the headquarters of the force in N'Djamena to report immediately to their posts, as it was almost ready to become operational.

Boko Haram has killed and kidnapped thousands of people in a six-year campaign to carve out an Islamic state from northeast Nigeria.

(Reporting by Madjiasra Nako; Editing by Daniel Flynn and Dominic Evans)