Police have identified the suicide bomber as 22-year-old Manchester resident Salman Abedi.
The attack took place at a concert of US popstar Ariana Grande at the Manchester Arena on Monday night.
Detectives are probing a “network” linked to Abedi, as the terrorist’s father insisted he is innocent.
Abedi’s father said: “We don’t believe in killing innocents. This is not us.”
Two of Abedi’s brothers, Ismail, 23, and Hashem, 18, and two other men have been arrested in connection with the bombing, while police are searching for a “bomb maker”.
Twenty victims remain in “critical care”, doctors said, with people suffering from “horrific injuries” including major organ damage and potential loss of limbs.
EARMARKED: Salman Abedi
According to US reports the bomber was identified by a bank card in his pocket.
Born in 1994, Abedi’s parents were Libyan refugees who fled to the UK to escape now deceased Muammar Gaddafi.
He attended Salford University in 2014 where he studied business management before dropping out.
His trips to Libya are now subject to scrutiny including links to jihadists.