(http://news.bbcimg.co.uk/media/images/80310000/jpg/_80310812_cameroonkolofata4641301.jpg) Chad previously had some troops based in Baga, a Nigerian town seized by Boko Haram earlier this month, but they had been withdrawn before the attack.
Correspondents say Nigerian politicians appear more focused on campaigning for elections next month than on security issues, and senior figures rarely comment on the insurgency in the north-east.
On Thursday, President Goodluck Jonathan made an unannounced visit to the area, his first for nearly two years.
He told displaced people in the biggest city of Borno state, Maiduguri, that he was "working very hard" to help them return to their homes.
Mr Jonathan's visit came as the human rights group Amnesty International released satellite images of towns attacked by Boko Haram, suggesting widespread destruction and a high death toll.
The pictures showed about 3,700 structures damaged or destroyed in Baga and neighbouring Doron Baga last week, the rights group said.
Amnesty's before-and-after satellite images were taken on 2 and 7 January.
Nigeria's government has disputed reports that as many as 2,000 people were killed in and around Baga, putting the number of dead at no more than 150.
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg) Boko Haram at a glance (http://news.bbcimg.co.uk/media/images/80142000/jpg/_80142357_afp_bh.jpg)
- Founded in 2002
- Initially focused on opposing Western education - Boko Haram means "Western education is forbidden" in the Hausa language
- Launched military operations in 2009 to create Islamic state
- Thousands killed, mostly in north-eastern Nigeria - also attacked police and UN headquarters in capital, Abuja
Who are Boko Haram? (http://www.theinfostride.com/news/world-africa-13809501)
Why Nigeria has not defeated Boko Haram (http://www.theinfostride.com/news/world-africa-27396702)
Boko Haram in numbers (http://www.theinfostride.com/newsbeat/30777607)
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg) (http://news.bbcimg.co.uk/media/images/80241000/gif/_80241077_boko_haram_civilian_death_624.gif)
Source: BBC