The United States has sent a team of experts to Nigeria to help find nearly 300 girls and women abducted from a school last month by the armed group Boko Haram.
US President Barack Obama described the kidnapping of the girls as "heartbreaking" and "outrageous", soon after residents said the group had seized eight more girls, aged between 12 and 15, again in the embattled northeast.
Obama urged global action against Boko Haram and confirmed Nigerian leaders had accepted an offer to deploy US personnel there.
The number of girls taken int he latest kidnapping has risen to 11, an official in the restive northeast said on Wednesday.
Residents initially said eight girls were taken when gunmen stormed a village in the Gwoza area of Borno state late on Sunday.
Gwoza official Hamba Tada told AFP the attackers snatched three more girls in a neighbouring village.
"After leaving Warabe the gunmen stormed the Wala village, which is five kilometres (three miles) away and abducted three more girls," he told AFP, referring to the two villages.
|Al Jazeera's Yvonne Ndege reports from Abuja where hundreds rallied in support of the missing girls.
The first group of girls was taken three weeks ago, and concerns have been mounting about their fate after Boko Haram chief Abubakar Shekau claimed responsibility in a video, saying his group was holding the schoolgirls as "slaves" and threatening to "sell them in the market".
Shekau criticised the female students for being taught "western education", which the Islamic group is avidly against. He also warned that his group planned to attack more schools and abduct more people.
Speaking to US broadcaster ABC, Obama said: "It's a heartbreaking situation, outrageous situation."
"This may be the event that helps to mobilise the entire international community to finally do something against this horrendous organisation that's perpetrated such a terrible crime," he added.
The team sent to Nigeria consists of "military, law enforcement, and other agencies", Obama said, and will work to "identify where in fact these girls might be and provide them help".
He denounced Boko Haram as "one of the worst regional or local terrorist organisations".
US officials have voiced fears that those abducted, who are aged between 16 and 18, have already been smuggled into neighbouring countries, such as Chad and Cameroon. The governments of both denied those abducted were in their countries.
Their fate has sparked global outrage and may constitute a crime against humanity according to the UN.
Parents of those taken said Shekau's video had made an already horrifying situation even worse.
"All along, we have been imagining what could happen to our daughters in the hands of these heinous people," one mother, Lawal Zanna, told AFP news agency by phone from Chibok.
The latest kidnappings also took place in Borno state.
We have no security here. If the gunmen decide to pick our own girls, nobody can stop them.
Abdullahi Sani, a resident of Warabe, said gunmen had moved "door to door, looking for girls" late on Sunday.
"They forcefully took away eight girls between the ages of 12 and 15," he said, in an account confirmed by other witnesses.
He said the attackers did not kill anyone, which was "surprising", and suggested that abducting girls was the motive for the attack.
Another Warabe resident, Peter Gombo, told AFP that the military and police had not yet deployed to the area.
"We have no security here. If the gunmen decide to pick our own girls, nobody can stop them."
Though initially slow to emerge, global outrage has flared over the mass abduction in Chibok, where Boko Haram stormed their school and loaded the girls at gunpoint onto trucks.
Several managed to escape but over 220 girls are still being held, according to police, with other sources saying the number is closer to 300.
British Foreign Secretary William Hague called the kidnappings "disgusting".
Egypt's prestigious Islamic institute Al-Azhar, which runs the main Sunni Islamic university in the region, said harming the girls "completely contradicts the teachings of Islam".