KANO, Nigeria - Four people were killed in the northeast Nigerian city of Potiskum on Sunday, when two female suicide bombers, one of them aged about 15, blew themselves up in a crowded market.
The blasts at the Kasuwar Jagwal mobile phone market in the commercial capital of Yobe State came just a day after a young girl thought to be aged only 10 killed 19 in Maiduguri, in neighbouring Borno State.
Also on Saturday, two people were killed when a car exploded outside a police station in Potiskum.
"We evacuated six bodies including those of the two female suicide bombers to the hospital. Twenty-one people were injured in the attacks.
A security source involved in the rescue operation told AFP of Sunday's bombings: "One of the bombers looked 23 and the other 15.
"The first bomber -- the 23 year-old -- detonated her explosives just outside the entrance of the market, where volunteers were sweeping people going inside the market with metal detectors.
"The second bomber was terrified by the explosion and she tried to dash across the road but she also exploded."
Both the security official and a nurse at the Potiskum General Hospital said six people were confirmed dead and 21 were injured.
Witness Ibrahim Dambam said the second blast went off as people fled the first.
Sunday is Potiskum's market day and attracts traders and shoppers from all over Yobe State and beyond.
Panicked shoppers fled and traders abandoned their stalls at both the mobile phone market and the city's main market, which is just next door.
Some security analysts believe that older women may willingly become human bombs as they share the Islamists' radical ideology or are out to avenge the death of loved ones at the hands of the military.
But the young ages of some of the bombers -- such as the girl in Maiduguri -- and the actions of the 15-year-old in Potiskum suggest that coercion is being used.
A civilian vigilante who witnessed the Maiduguri bombing said of the young bomber: "I doubt if she actually knew what was strapped to her body."
Another eye-witness said it appeared that the bomb was remote-controlled, which chimes with testimony from other attacks across the wider north of Nigeria.