Witnesses to the aftermath of a stabbing attack in central London, where one woman died and up to five others were injured have described seeing body bags lying in the street.
A woman believed to aged in her 60s was killed and five others - reported to be one woman and four men - were injured in the Wednesday night attack in Russell Square in Bloomsbury. The full extent of their injuries is not yet known.
A 19-year-old man was arrested within minutes and remains under police guard in hospital.
"Terrorism is one possibility being explored at this stage," UK police said in a statement.
A British woman calling herself Lauren told AAP her brother was among a group of University College London students walking back to campus from the nearby Gielgud Theatre when "they heard a scream".
"They then saw the man run past them very quickly ... the woman was out with a group of friends and they saw her lying in the street," she said.
Her brother told her he believed some of those who were attacked were on a hen's night.
Central London resident Eric Patrick Andrew said he watched police and ambulances flood the crime scene.
"An army of police and ambulance plus what look like body bags," he posted on Facebook.
London taxi driver Paul Hutchinson told The Daily Mail he could see a "body was just lying on the floor".
"You could see the boots sticking out from under the cloth," he said.
A crime scene has been set up with a police cordon around Russell Square.
