MAIDUGURI, Nigeria (AP) — A bomb wounded four people Sunday in a market in Maiduguri, a day after 30 people were killed in the northeastern Nigerian city by a suicide bomber and attackers firing rocket-propelled grenades.

The Boko Haram militant group is suspected in the attacks which followed Friday’s inauguration of President Muhammadu Buhari, who said he is moving the headquarters for the Nigerian military’s fight against the extremists to Maiduguri from the capital of Abuja.

Sunday’s blast came from explosives concealed in bags of charcoal at the Gamboru market, said trader Jafar Aminu.

“The explosion did not kill anyone but injured four persons, including one whose arm was completely ripped off by the blast,” Aminu said.

The market in Maiduguri, the capital of Borno state, has been hit by several attacks that have killed dozens of people in the past three years.

Maiduguri is the birthplace of Boko Haram, which for nearly six years has led an Islamic uprising in northeastern Nigeria that has killed an estimated 13,000 people in a campaign of bombings, hit-and-run attacks and abductions.

A multinational offensive this year forced the insurgents from towns where they had declared an Islamic caliphate.

Nigeria’s military says Boko Haram’s main fighting force is trapped in the northeastern Sambisa Forest. But the insurgents keep attacking Maiduguri, which is 200 kilometers (125 miles) away.

Maiduguri’s population of 2 million has swelled with hundreds of thousands of refugees who have been forced from their homes.

Thirteen people were killed Saturday in Maiduguri when Boko Haram fighters fired rocket-propelled grenades on the western outskirts — a new tactic that destroyed several homes, according to witnesses.

Later Saturday, a suicide bomber blew himself up outside a Maiduguri mosque, killing 16.

Also Sunday, the insurgents attacked the town of Fika in the neighboring state of Yobe. No one was killed, but several government offices were burned down and shops were looted, said local merchant Modu Fika.

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Associated Press writers Michelle Faul in Abuja, Nigeria, and Adamu Adamu in Damaturu, Nigeria, contributed to this report.

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