US Secretary of State John Kerry on Tuesday offered to send experts to Nigeria to help track down the more than 200 schoolgirls kidnapped by suspected Boko Haram Islamists.
Kerry made the offer in a phone call to Nigeria's President Goodluck Jonathan, State Department spokeswoman Jen Psaki said, only a few hours after residents said the extremist group had seized eight more girls, aged between 12 and 15.
Nigeria has already accepted an offer from Washington to set up a coordination cell at its Abuja embassy with US military personnel and law enforcement officials, said Psaki.
The girls taken on Tuesday were seized by gunmen in the village of Warabe just one day after Boko Haram chief Abubakar Shekau claimed responsibility for the the mass kidnapping in the nearby town of Chibok three weeks ago, which has sparked global outrage and may constitute a crime against humanity according to the UN.
Shekau said his extreme Islamist group was holding the schoolgirls abducted on April 14 as "slaves" and threatened to "sell them in the market", in a video obtained by AFP on Monday.
The parents of those taken from Chibok 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," Lawal Zanna, the mother of one the hostages, told AFP by phone from Chibok.
"Now Shekau has confirmed our fears," he said.
The latest kidnappings also took place in Borno state, a stronghold of the Islamist group.
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."
- Outrage builds -
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.
British Foreign Secretary William Hague on Tuesday called the kidnappings "disgusting" while US senators urged Washington to intervene.
Angelina Jolie, speaking in Paris, condemned the Chibok abductions as "unthinkable cruelty and evil".
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".
Since the attack, parents have criticised the military's rescue mission, saying there had been a lack of urgency from the outset.
Enoch Mark, an outspoken critic of the authorities since his daughter was kidnapped in Chibok, said "the government should find our girls or seek international assistance if it cannot".
"Boko Haram are not spirits or extra-terrestrial creatures that cannot be tracked and subdued," he told AFP by phone. "The agony and trauma are becoming too much for us parents to bear."
The military said it had launched a major search operation, including in the Sambisa Forest area of Borno where Boko Haram has well-fortified camps.
There are indications the girls may have been moved across Nigeria's borders, the US State Department said, echoing unconfirmed reports from local leaders in Chibok who claimed the hostages had been sold as brides to Islamist fighters in Cameroon and Chad.
The governments of Chad and Cameroon both denied the girls were in their countries.
"The reports that 223 teenagers abducted by Boko Haram have been taken to Chad is baseless," said Chad's communications ministry in a statement. "Steps are being taken to ensure the security of our borders with neighbouring countries."
Cameroon's Minister of Communication Issa Tchiroma Bakari said the claims were "groundless".
- President under pressure -
As well as mounting pressure over the kidnappings, Nigerian President Goodluck Jonathan must also contend with a spate of terrorist attacks, including a car bomb that ripped through a crowded bus station on the outskirts of Abuja just a few hours before the mass abduction leaving 75 dead -- the deadliest-ever attack in the capital.
A copycat bombing at the same station killed 19 people on May 1.
Jonathan had hoped that a World Economic Forum summit which opens in Abuja on Wednesday would highlight Nigeria's economic progress and underline its recent emergence as Africa's biggest economy.
But it is Boko Haram's extreme violence that has dominated headlines, with many questioning whether Nigeria has the capacity to contain the insurgents who have killed thousands since 2009, and at least 1,500 this year alone.
The group, which says it wants to create an Islamic state in mainly Muslim northern Nigeria, has vowed to carry out further attacks across the country, including in the Niger Delta, home to Africa's largest oil industry.