(http://news.bbcimg.co.uk/media/images/79238000/png/_79238489_nigeria_damasak_464.png) Chadian army Col Azem Bermandoa Agouna told AFP news agency that he had seen "about 100 bodies spread under a bridge just outside the town".
Together with the Nigerian army, forces from Chad, Niger and Cameroon are involved in an offensive against the Islamist insurgents who began taking over territory about a year ago - after being pushed out of their base in Maiduguri.
Nigeria is preparing to hold presidential elections on 28 March after security concerns led to a postponement of the original date in mid-February.
'Under-rated external influence' President Jonathan's government has been heavily criticised for its failure to end the six-year insurgency in the north-east.
He admitted that the government has been surprised by the group's progress.
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg)
Boko Haram at a glance:(http://news.bbcimg.co.uk/media/images/81618000/jpg/_81618962_fb476f58-526d-4641-9329-605265cd4638.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 an Islamic state
- Thousands killed, mostly in north-eastern Nigeria - has also attacked police and UN headquarters in capital, Abuja
- Abducted hundreds, including at least 200 schoolgirls
- Controls several north-eastern towns
- Launched attacks on neighbouring states
Can regional force beat Boko Haram? (http://www.bbc.co.uk/news/world-africa-31695508)
Why is Boko Haram so strong? (http://www.theinfostride.com/news/world-africa-30933860)
(http://news.bbcimg.co.uk/media/images/75306000/jpg/_75306515_line976.jpg) "We never expected that [Boko Haram] will build up that kind of capacity. We under-rated their external influence. Since after the civil war we've not fought any war, we don't manufacture weapons, so we had to look for help to re-equip our army and the air force," he told the BBC.
The government has made similar claims in the past about defeating or driving back Boko Haram within a specific period - but these have not been borne out by events.
Boko Haram promotes a version of Islam which makes it "haram", or forbidden, for Muslims to take part in any political or social activity associated with Western society.
Earlier this month, the group pledged allegiance to Islamic State militants, who control large parts of Syria and Iraq and are also active in Libya.
The violence in north-eastern Nigeria has killed more than 15,500 people since 2012.
Source: BBC