British police are hunting for accomplices who may have helped Salman Abedi build a suicide bomb which killed 22 people at a concert in Manchester on Monday, a source with knowledge of the investigation said.

“The question is: Was he acting alone or was he part of a network of others who want to kill. That is what the investigation is focusing on," the source, who spoke on condition of anonymity, told Reuters.

“The concern is that there may be others out there who helped him to make the bomb. Making a bomb of this sort requires a certain level of expertise and competence," the source.