Updated

Militants from the Islamic terror group Boko Haram have made good on their leader's chilling threat, kidnapping eight more girls from a Nigerian village late Monday, authorities said.

The abductions came hours after Boko Haram leader Abubakar Shekau was seen on a widely-circulated video vowing to continue kidnapping the daughters of Christians, forcing them to convert to Islam and selling them into slavery. The kidnappings brought to more than 300 the number of girls who have been taken, according to Nigerian police.

Police said the girls, reportedly ranging in age from 12 to 15, were taken on trucks, along with livestock and food from the village of Warabe, in the nation's northeast.

"They were many, and all of them carried guns. They came in two vehicles painted in army color. They started shooting in our village,'' Lazarus Musa, of Warabe, told Reuters.

Shekau, whose group's name translates to "Western education is sinful," took credit for the kidnapping of the girls in the hour-long video that opens with Boko Haram fighters firing guns into the air and shuoting Allahu Akhbar!"

"I abducted your girls," he said. "By Allah, I will sell them in the marketplace," he said in the video.

President Obama reacted to the kidnappings Tuesday in an interview with ABC, calling them “heartbreaking” and “outrageous.”

“You’ve got one of the worst regional or local terrorist organizations in Boko Haram in Nigeria, they’ve been killing people ruthlessly for many years now and we’ve already been seeking greater cooperation with the Nigerians – this may be the event that helps to mobilize the entire international community to finally do something against this horrendous organization that’s perpetrated such a terrible crime,” Obama said.

On Tuesday, the White House said U.S. Secretary of State John Kerry had spoken with Nigerian President Goodluck Jonathan, who welcomed Kerry's offer of a U.S. team to provide support. The U.S. has said it stands ready to send a team of American military and law enforcement personnel to aid in the hunt for kidnap victims.

Kidnapped girls have reportedly been forced to marry their abductors — who paid a nominal bride price of $12 — or taken to neighboring Cameroon and Chad. An intermediary has told Nigeria's government that the terror group is willing to negotiate ransoms for the girls, and that two have died from snakebites and several more are ill. More than 280 remain in captivity and 53 have escaped, according to Nigerian police.

One 16-year-old Nigerian girl who was present during the mass abduction at the Chibok Government Girls Secondary School on April 15 recalls the students were at first happy to see gunmen.

The girls in the school dorm could hear the sound of gunshots from a nearby town. So when armed men in uniforms burst in and promised to rescue them, at first they were relieved.

"Don't worry, we're soldiers," the girl, who later escaped, recalled them saying. "Nothing is going to happen to you."

The gunmen commanded the hundreds of students at the Chibok Government Girls Secondary School to gather outside. The men went into a storeroom and removed all the food. Then they set fire to the room.

"They ... started shouting, `Allahu Akhbar,' (God is great)," the 16-year-old student said. "And we knew."

The terrorists kidnapped the entire group of girls and drove them away in pickup trucks into the dense forest.

Their plight -- and the failure of the Nigerian military to find them -- has drawn international attention to an escalating Islamic extremist insurrection that has killed more than 1,500 so far this year.

The military says it is diligently searching for the girls, with extensive aerial surveillance.

"Every information relayed to security agencies has so far been investigated, including the search of all places suspected as a possible hide-away of the kidnapped girls," Information Minister Labaran Maku said Friday.

But many soldiers have told the AP they are demoralized, because Boko Haram is more heavily armed and better equipped, while they get little more than a meal a day. In the meantime, the parents are frantic. Through sobs and jagged gasps for air, the mother of a missing 15-year-old said she had lost confidence in the authorities.

"I am so very sad because the government of Nigeria did not take care of our children and does not now care about our children," said the mother, who spoke on condition of anonymity to protect her daughter. "All we have left is to pray to God to help them and help us."

The Associated Press contributed to this report. 

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