(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-style 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 - has also attacked police and UN headquarters in capital, Abuja
- Has abducted hundreds, including at least 200 schoolgirls
- Controls several north-eastern towns
- Has launched attacks on Cameroon
Why is Boko Haram so strong? (http://www.theinfostride.com/news/world-africa-30933860)
Soldiers without weapons (http://www.theinfostride.com/news/magazine-30930767)
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg) According to evidence gathered by Amnesty International, commanders at the military base in Baga, in the far north-east of Nigeria, regularly informed military headquarters in November and December 2014 of the threat of a Boko Haram attack and repeatedly requested reinforcements.
There were also warnings that the town of Monguno, about 140km (85 miles) north of Maiduguri city which was captured by Boko Haram on Sunday, would be attacked.
"Everyone was aware," a Monguno resident told Amnesty.
"Boko Haram came on Wednesday last week [21 January] and asked the villagers [in nearby Ngurno] to leave because they are coming to attack the barracks. The villagers told the soldiers."
Amnesty International's Africa director Netsanet Belay said the attacks were an "urgent wake-up call for the Nigerian leadership, the African Union and the international community".
Maj Gen Olukolade said in operational areas surveillance would have been continuous to ward off attacks.
Earlier this month, Chadian soldiers deployed to Cameroon's border with Nigeria to help secure the porous border.
African Union heads of state are going to include the conflict in north-eastern Nigeria on the agenda of their summit, due to begin on Friday.
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg) Capture of Baga (http://news.bbcimg.co.uk/media/images/80590000/jpg/_80590979_bagaoverview_624.jpg) Satellite images show the destruction in Baga and Doron Baga after the Boko Haram assaults
3 January: Social media reports of Baga attack first emerge
4 January: Boko Haram claims to have captured Baga
8 January: Reports emerge of bodies strewn on the streets in Baga, with some saying 2,000 people killed
12 January: The government says that the number of people who lost their lives in Baga was no more than 150, including militants
15 January: Satellite images released by Amnesty International suggest the number of dead is far higher than officially admitted
Fleeing Baga over Lake Chad (http://www.bbc.co.uk/news/world-africa-30900915)
Why it is hard to know the truth in Nigeria (http://www.bbc.co.uk/news/world-africa-30794829)
Source: BBC