Nigeria’s police have offered a $300,000 (£180,000) reward to anyone who can help locate and rescue more than 200 abducted schoolgirls.
They were kidnapped more than three weeks ago by Islamist Boko Haram militants from their boarding school in the north-eastern state of Borno.
The militants have been blamed for another attack on a town in the state on Monday, a busy market day.
A senator from the remote area said some 300 people had died in the raid.
Ahmed Zanna said the gunmen arrived in a convoy of vans in Gamboru Ngala, near the border with Cameroon.
They stole food and motorbikes, burned hundreds of cars and buildings during their rampage, the politician told the BBC’s Hausa service.
A town resident, who asked not to be named, told the BBC that as the call for Muslim prayer was heard at about 13:00 local time (12:00 GMT) on Monday, gunshots could also be heard.
He said the attackers were Islamist insurgents as they were shouting “Allahu Akbar [God is great].”
The attack lasted for about five hours and the town was busy with traders from other areas, he said.
Correspondents say it often takes time for news of such attacks to spread as mobile phone networks can be affected by the security crackdown in the region.
The market raid is the latest attack to be blamed on Boko Haram, whose leader admitted earlier this week that his fighters had abducted the girls in the middle of the night from their school in the town of Chibok on 14 April.
Abubakar Shekau threatened to “sell” the students, saying they should not have been in school in the first place, but rather should get married.
The group, whose name means “Western education is forbidden” in the local Hausa language, began its insurgency in 2009.
More than 1,500 are said to have been killed in the violence and subsequent security crackdown this year alone.
A statement from the police said the 50m naira reward would be given to anyone who “volunteers credible information that will lead to the location and rescue of the female students”.
Six telephone numbers are provided, calling on the general public to be “part of the solution to the present security challenge”.
“The police high command also reassures all citizens that any information given would be treated anonymously and with utmost confidentiality,” the statement said.
Another 11 girls were kidnapped on Sunday night after two villages were attacked near the militants’ forest hideout.
The abductions have prompted widespread criticism of the Nigerian government and demonstrations countrywide.
The BBC’s Mansur Liman in the capital, Abuja, says many are questioning why it has taken so long for such a reward to be offered.
The girls are mostly aged between 16 and 18 and were taking their final year exams.
The governments of Chad and Cameroon have denied suggestions that the abducted girls may have already been smuggled over Nigeria’s porous borders into their territory.
A team of US experts has been sent to Nigeria to help in the hunt.
On Tuesday, US President Barack Obama described the abductions as “heart-breaking” and “outrageous” and said he hoped the kidnapping might galvanise the international community to take action against Boko Haram.
Security has been tightened in Abuja as several African leaders and Chinese Premier Li Keqiang are attending the World Economic Forum for Africa in the city, where two recent attacks have been blamed on the insurgents.