YAOUNDE, Cameroon — Nigeria’s Boko Haram Islamic extremists have abducted about 30 people, including eight Cameroonian girls, and killed seven hostages in two bus hijackings in Cameroon and Nigeria, Cameroon residents and a Nigerian intelligence officer said Tuesday.

Boko Haram, who kidnapped nearly 300 schoolgirls in Nigeria last year in an incident that ignited international outrage, have taken eight Cameroonian girls hostage, said Chetima Ahmidou, the principal of a school in the area. The girls range in age from 11 to 14 and come from the town of Koza, he said.

The bus attack took place Sunday about 11 miles from Cameroon’s border with Nigeria. Seven other hostages were slain and their bodies scattered near the border, said Ahmidou, whose brother was the bus driver and was among those killed.

Also Sunday, across the border in Nigeria, the Islamic extremists held up a bus in Akada-Banga village of Bama district and made off with about 20 people, including women and children, according to a security officer who spoke on condition of anonymity because he is not authorized to give information to reporters.

Boko Haram has fought a 5-year insurgency against the Nigerian government, launching scores of attacks that left 10,000 people dead last year alone. In recent weeks, the terror group has intensified its assaults on neighboring Cameroon and Niger. Together with Nigeria’s other neighbors, Benin and Chad, they have pledged to form an 8,750-strong multinational force to confront the Islamic extremists.

On Monday, Niger’s parliament voted to approve supporting the mission. The vote came just hours after a car bombing in the town of Diffa, which was blamed on Boko Haram, who had launched three other attacks on the town since Friday.

The United Nations said Tuesday that a team of five experts from its peacekeeping department has deployed to provide support in readying the force.