Theresa May has said the official terror threat level will be assessed throughout the day in the wake of the Manchester attack.
The assessment for international terrorism in the UK currently remains at severe.
What we know so far:
- 22 people have been killed and 59 injured in the blast.
- There are many children and young people among the dead.
- The attack was carried out by a lone male suicide bomber who detonated an improvised explosive device. He died at the arena.
- Security services believe they know his identity and are investigating whether he acted alone or was part of a network.
- A 23-year-old has been arrested in South Manchester in connection with the incident.