An insurgent attack in a Nigerian town has killed 300 people after the town was left unprotected following the redeployment of soldiers to find 223 missing schoolgirls.

The attack targeted the town of Gamboru Ngala on Nigeria’s border with Cameroon, where gunmen this week razed scores of buildings and fired on civilians as they tried to flee.

Area Senator Zanna said the town had been left unguarded because the soldiers based there had been redeployed north towards Lake Chad in an effort to rescue the school girls kidnapped by Boko Haram on April 14.

The latest attack is also believed to have been carried out by Boko Haram, a militant Islamist group whose named loosely translates to “Western education is sinful”.

News of the attack comes as Nigerian police announced a 50 million naira ($A324,600) reward for information leading to the rescue of more than 200 schoolgirls held hostage by the Islamists.

“The Nigeria Police hereby announce a cash reward of 50 million naira to anyone who volunteers credible information that will lead to the location and rescue of the female students abducted from Government Girls Secondary School, Chibok, Borno State,” a statement on Wednesday said, referring to the April 14 mass abduction claimed by the Islamist extremists.

The shocking mass abduction has sparked global outrage and offers of help from the United States, Britain, France and China.

Nigeria’s response to the kidnappings has been widely criticised, including by activists and parents of the hostages who say the military’s search operation has been inept so far.

President Goodluck Jonathan’s administration has sought to appear more engaged with the plight of the hostages in recent days, especially after Boko Haram chief Abubakar Shekau released a video threatening to sell the girls as “slaves”.

In a second kidnapping, eleven more girls aged 12 to 15 years were seized on Sunday from Gwoza, an area not far from Chibok and also in Borno state, Boko Haram’s base.

US President Barack Obama has described the Chibok abductions as “heartbreaking” and “outrageous”, and announced that a team of military experts had been sent to help Nigeria’s rescue mission.

First Lady Michelle Obama has also tweeted in support of the search, which has also received assistance from Britain.

.@FLOTUS tweets in support of missing Nigerian girls pic.twitter.com/oqgKJu2eo9 http://t.co/Gs9ZIslok4 #BringBackOurGirls

— Huffington Post (@HuffingtonPost) May 7, 2014

Analysts said Jonathan’s acceptance of Western military assistance suggested an admission he can no longer manage the Boko Haram uprising without help.

-with AAP