Another three people have been arrested in connection to the Manchester bombing which killed 22 people, including a number of children.
A man has also been arrested outside Buckingham Palace with a knife on Wednesday morning, but police say it's not thought to be terror-related or linked with the Manchester attack.
UK Prime Minister Theresa May increased the terror threat level to critical in response to the Manchester attack, suggesting a further attack is "imminent".
Armed soldiers have been deployed to the streets amid fears the attacker, who died in the blast, wasn't acting alone.
A 23-year-old man was arrested on Tuesday and remains in custody.
On Wednesday morning, Greater Manchester Police confirmed another three men had been arrested in the south of the city linked to the attack.
The bombing targeted an Ariana Grande concert, exploding near the exits just after the show finished.
Twenty two people were killed and another 59 injured, many of whom remain in a critical condition.
The youngest victim identified so far was an eight-year-old girl.
Police aren't yet sure whether the bomber acted alone or whether there is a risk of further attacks.
A number of homes have been searched in south Manchester as the investigation continues.