A 17-year-old was stabbed to death while another was injured in an attack by their rivals in Dhaka's Sutrapur area on Monday night.
The victim Ananto, a resident of Dholaikhal's Lalchan area, was a ninth-grader at a local school.
Dhaka Medical College and Hospital (DMCH) police outpost's Assistant Sub-Inspector Abdul Khan said a critically injured Ananto was declared dead by the on-duty physician at the hospital.
The body has been kept at the Dhaka Medical College morgue for autopsy.
Injured Saju Ahmed, 14, is undergoing treatment at the hospital, he added.
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Sarwar, a friend of the victim, said a group of eight to nine teenagers, including Ananto, was returning home after prayers on the night of Shab-e-Barat.
On the way, they found 10 to 12 teenage boys were beating up Saju in Farajganj Ghat area around 11pm.
As Ananto rushed there to rescue Saju, one of the assaulters, Ferdous stabbed him several times.
The perpetrators fled the scene before others reached to help Ananto and Saju, said Sarwar.
Quoting Saju, one of his friends said Saju was attack following a quarrel with Ferdous and one Alamin.
There is a rising trend of teen-gang culture in Dhaka and elsewhere of the country. The gang members are involved in several types of crimes, ranging from mugging, stalking, hijacking, extortion, murder, drug trading, abuse, and so on.