Boko Haram’s leader, Abubakar Shekau, said in a video sent to reporters Sunday that it is  responsible for the June 25 blast at a fuel depot in Lagos and another in the capital, Abuja, that left at least 21 people dead. Shekau went on to mock calls for the release of more than 200 schoolgirls his group abducted in April, saying the government must free detained Islamist fighters in exchange.

“We were the ones that detonated the bomb in Abuja, that filthy city; we’re the ones that sent a female bomber to the refinery in Lagos,” Shekau said in the video, surrounded by several armed men, with armored vehicles in the background. “Nigerians are saying bring back our girls, let them bring back our own soldiers.”

Boko Haram, whose name means “Western education is a sin” in the local Hausa language, wants to impose Shariah, or Islamic law, in Africa’s most populous country. The nation of about 170 million people is roughly split between a mainly Muslim north and a predominantly Christian south.

Most of its attacks have been in the northeast, where most victims are poor Nigerians in villages and markets. Three bombs have exploded in Abuja this year, killing more than 100 people. Lagos, the nerve center of Nigerian investment and business had not suffered bombings has until the June attack.

Nigerian security forces are struggling to contain Boko Haram attacks. Three northeastern states have been under emergency rule since May 2013, and foreign governments are assisting the Nigerian effort to find the kidnapped schoolgirls.

Showing off weapons he said his group captured in an attack on the military, Shekau mocked President Goodluck Jonathan and expressed solidarity with other Islamist leaders including Abu Bakr al-Baghdadi, whose Islamic State of Iraq and Syria has capture large portions of Iraq and Syria.

Malala Yousafzai, the Pakistani schoolgirl who survived a Taliban gun attack two years ago to become a global advocate for girls’ education, said during a visit to Nigeria that Jonathan promised to return the girls to their families.

“Even though the promises have been made, it does not mean that I will stop my campaign,” she told reporters in Abuja after meeting Jonathan. “I will be counting days and I will be looking when those girls are returning back home. I will continue this campaign until I see those girls going back to school, returning to their families and continuing their education.”