The attack and hundreds of casualties were confirmed by Borno state information commissioner Mohammed Bulama, who spoke to The Associated Press by telephone Wednesday.
Nigerian federal Senator Ahmed Zannah blamed fighters of the Boko Haram terrorist network, which has claimed responsibility for the April 15 kidnapping of 276 teenage girls from their boarding school in Chibok, in northeastern Borno state. The insurgents threatened to sell the young women into slavery in a video.
The Obama administration announced Tuesday it was sending personnel and equipment to help Nigerian security forces in their search for the girls in the vast Sambisa Forest.
Nigerian President Goodluck Jonathan confirmed that he has accepted the U.S. assistance, which the Pentagon said Wednesday will help with communications, logistics and intelligence planning, but will not include any military operations.
Britain and China announced Wednesday that Nigeria has accepted their offers of help. France said it was sending in a "specialized team" to help with search and rescue of the girls.
"In the face of such an appalling act, France, like other democratic nations, must react," French Foreign Minister Laurent Fabius said. "This crime will not go unpunished."
Fabius gave no details, except to say the team was being drawn from forces already in the region. France has soldiers in Niger, Cameroon and Mali, where it is fighting Islamic insurgents, as well as in Central African Republic.
The kidnapping has ignited a viral social media campaign under #BringBackOurGirls that has brought renewed attention to Boko Haram's campaign of violence. On Wednesday, first lady Michelle Obama joined in, tweeting, "Our prayers are with the missing Nigerian girls and their families."
Boko Haram's five-year-old Islamic uprising has claimed the lives of thousands of Muslims and Christians, including more than 1,500 people killed in attacks so far this year. The group, whose name means "Western education is sinful," has tried to root out Western influence by targeting schools, as well as attacking churches, mosques, government buildings and security forces in the country of 170 million, divided between a predominantly Christian south and Muslim north.