One woman has died and two others are seriously ill in hospital after a fight involving five women.
Police said they were called to a dispute at a flat on Peckham Road, Camberwell, south London, at 2115 BST on Wednesday.
Three women with stab wounds were found inside the flat.
One of the women, aged in her 30s, died at 2300 BST in hospital and the other two are in a serious condition. Police are questioning two women.
They are being held in custody at separate police stations in south London.
Police have started a murder investigation and appealed for witnesses.
A post-mortem examination is due to be held at Greenwich Mortuary.