A 27-year-old woman was arrested in Karachi's Sikanderabad area on Friday for allegedly murdering her husband's second wife, police said.

Newlywed Fatima, 17, was asleep in her home when Shahnaz allegedly attacked her with a knife and killed her as her six-year-old daughter looked on, Station House Officer Shaoor Khan said.

Shahnaz later informed her husband Muhammad Juman over the phone that she was leaving the house, the SHO said.

Police, acting upon information provided by Juman, arrested the suspect near a petrol pump in the area as she was trying to flee, he said.

The SHO said that Juman, a gardener, had entered into a love marriage with the victim two months ago.

Shahnaz is yet to make a statement on the motive of the murder, he added.