Islamic extremists Saturday claimed responsibility for the massive rush-hour explosion earlier this week that ripped through a busy bus station in Nigeria's capital, Abuja, killing at least 75 people and wounding 141.

"We are in your city, but you don't know where we are," Abubakar Shekau, leader of the Boko Haram terrorist network, says in a new video that threatens more attacks.

"Yes, we are the ones who carried out the attack in Abuja," he says in Nigeria's Hausa language in the video, which was received through the same channels as previous ones.

Shekau makes no mention of the abductions of more than 100 girls and young women from a remote northeastern school hours after the bomb blast, also blamed on his fighters.

Officials say dozens of the girls have managed to escape, but 85 remain unaccounted for.

Parents and townspeople have joined security forces and vigilantes searching the Sambisa Forest for the kidnapped girls — an area dangerous because it is known to contain hideouts of the militants. Borno state's education commissioner, Musa Inuwo Kubo, said Friday that the girls who escaped have been sent to their homes all over the state for their own safety because there was no security, not at the school and not in Chibok town. It was unclear why the military haven't deployed troops at least to the school, where the girls have been brought once they escape. Some managed to jump off the back of the truck into which they were bundled in the dark of the pre-dawn attack. Others have escaped from an apparent militant camp, wandering in the bush until they are found.

Monday's explosion in Abuja, just a 15 minutes' drive from the presidential villa, was the first attack in two years on the capital, which is in the heart of the country and hundreds of miles (kilometers) from the militants' traditional stronghold in the northeast. The toll is expected to rise when pathologists say how many people were blown apart by the mighty blast that blew a hole 4-feet (1.2 meters) deep in the dirt of the Nyanya Motor Park.

It undermined government and military claims that they have contained the Islamic uprising to the extreme northeast of the country, and raised fears that the insurgency is spreading.

President Goodluck Jonathan declared a state of emergency in May 2013 and flooded the area with troops who speedily drove the extremists out of towns and villages. But they have been struggling for months now to dislodge the extremists from hideouts in the forest and in mountain caves along the border with Cameroon.

Boko Haram — the nickname means "Western education is sinful" — says Western education and influence have corrupted Africans and only Islamic law can save Nigeria from endemic corruption that is impoverishing citizens of Africa's biggest oil producer and it's economic powerhouse. Nowhere is poorer than the northeast, the birthplace of Boko Haram where only about 5 percent of children finish high school, and only a tiny percentage of those are female.