Police in Brixton said the man they have arrested following a fatal stabbing where a 28-year-old woman was killed trying to protect her younger sister, is known to them, but would not give any more details.
Speaking this afternoon, Detective Reynolds said young children were at the scene of both attacks, which involved "extreme violence", and officers are trying to establish whether they saw anything significant.
More top news
A group of soldiers has broken an Antarctica record by becoming the first all-female team to cross the continent using only muscle power.
Gunmen have attacked the Intercontinental Hotel in Kabul with casualties feared.
The Grammy-winning singer posted a picture of the two on his Instagram saying the two got engaged right before the new year.