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, burning hundreds of cars and buildings during their rampage, the politician told the BBC's Hausa service.
Mr Zanna and several residents said the gunmen had used a diversionary tactic to get the security forces out of Gamboru Ngala by spreading rumours that the abducted schoolgirls had been spotted somewhere else.
The security forces then left, leaving residents at the mercy of the attackers, they said.
Boko Haram's leader admitted earlier this week that his fighters had abducted the girls 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.
An estimated 1,000 people have died in the violence and 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" and promising confidentiality.
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 resident of Gamboru Ngala told the BBC 310 people had been buried on Tuesday and Wednesday, following Monday's attack.
"At the big cemetery of Gamboru Ngala, I recorded 165 buried. At the small graveyard, I recorded 145 graves. But we are still picking corpses from the main market. Many people locked themselves up in the market when the attacks started so they got burnt in their shops," he said.
The militants had locked up whole families in their homes, and then would enter and spray them with bullets, another resident said.
The gunmen were shouting "Allahu Akbar [God is great]", as they stormed the remote town in Borno state, the resident added.
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.
On Tuesday, US President Barack Obama said he hoped the kidnapping might galvanise the international community to take action against Boko Haram.
The US has despatched a team of experts to Nigeria.
On Thursday, the UK said it was also sending a small team to provide the government with planning and co-ordination advice. The team should be on the ground within days.
Security has been tightened for the World Economic Forum for Africa, in Abuja, where two recent attacks have been blamed on Boko Haram.