A gang of miscreants stabbed Dihan indiscriminately near his residence at Shehora Munshibari, leaving him critically injured, said Khandaker Shaker Ahmed, officer-in-charge (investigation) of Kotwali Police Station.
A man in his 20s has been arrested on suspicion of murder over the Brixton attack and is now in custody.
The woman, aged in her 30s, was killed in an incident in Sudbourne Road, Brixton on Sunday evening.
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Police and paramedics were called to Chestnut Avenue where they found the 18-year-old suffering from knife wounds at around 10.50pm.
The stabbings come as the number of killings so far this year approaches 60 in London.
In relation to the Brixton incident, police arrested a man in his 20s on suspicion of murder. She was confirmed dead at a hospital about one hour later.