Kano, Nigeria - At least 30 people were killed when suspected members of Islamist extremist sect Boko Haram bombed a bridge linking Nigeria to Cameroon, the newspaper Punch reported on Friday.

The bomb went off on Thursday evening on the outskirts of the village of Gamboru Ngala, where more than 200 people were killed and 11 girls kidnapped by Boko Haram this week.

“I believe some people are still trapped in some debris,” resident Gamboru Ngala told the newspaper.

Meanwhile, the hunt for more than 200 schoolgirls abducted more than three weeks ago by Boko Haram in northern Nigeria continues.

A US emergency team headed to Africa's most populous nation to help find the girls, while Britain, China, France and Canada also pledged their support.

The US State Department said that the military officials will arrive in Nigeria within three days. In addition, an unspecified number of hostage negotiation and forensic experts will be sent from the FBI. The teenage girls were abducted on April 14 from a boarding school in the town of Chibok, near Borno state capital Maiduguri.

Boko Haram leader Abubakar Shekau threatened to sell and enslave the girls. It was unclear how many were still in captivity, with some having escaped.

Nigerian police offered a reward of 50 million naira to anyone providing a lead on the whereabouts of the abducted children.

Global outrage against the abduction grew on Friday, with tens of thousands of people around the world, including US First Lady Michelle Obama, joining the #BringBackOurGirls social media campaign to protest the abductions.

The UN Human Rights Office warned Boko Haram, which means “Western education is sinful”, that its actions may be judged as crimes against humanity, a label for severe and systematic acts of violence.

UN Secretary General Ban Ki-moon spoke to President Goodluck Jonathan and expressed “deep concern” over the kidnapping of the schoolgirls. - Sapa-dpa