US experts have arrived in Nigeria to help rescue more than 200 schoolgirls being held hostage by Boko Haram Islamists, an embassy spokeswoman says.

“They are here…the team is on the ground,” Rhonda Ferguson-Augustus said, without specifying the precise make-up of the group.

US officials have previously said Washington would send military personnel as well as specialists from the Justice Department and the FBI.

Britain, France and China have also offered varying levels of assistance, including planning and co-ordination specialists as well intelligence and satellite imagery.

Speaking at the World Economic Forum in Nigeria’s capital Abuja on Friday, President Goodluck Jonathan restated that his country was “totally committed to getting these girls back”.

Nigeria’s initial response to the April 14 mass abduction in the northeastern town of Chibok was widely criticised, and for several days Jonathan said very little about the shocking attack.

But this week outrage over the girls plight has spread across the world, helped by a growing social media campaign with the hashtag #BringBackOurGirls.

The campaign has drawn support from celebrities and prominent personalities ranging from US First Lady Michelle Obama to the actress Angelina Jolie.

A chilling video by Boko Haram’s leader Abubakar Shekau, in which the wanted Islamist leader threatened to sell the hostages “in the market”, has also raised awareness about the attack.

As global concern has mounted, top Nigerian officials have sought to appear more engaged with the rescue effort.

National Security Adviser Sambo Dasuki, top army brass and police chief Mohammed Abubakar made a joint visit on Thursday to Chibok, which falls in Nigeria’s restive and deeply impoverished northeast, where Boko Haram was founded more than a decade ago.