Manchester bombing: Terror 'network' was behind suicide attack, say police

Police investigating the Manchester Arena suicide bomb attack are convinced they are dealing with a "network" of terrorists, a senior officer has said.

Following the explosion that killed 22 people and injured 64 outside a concert by pop star Ariana Grande, Theresa May announced that the UK terror threat level had been raised to "critical", meaning an attack is expected imminently.

And Ian Hopkins, the Chief Constable of Greater Manchester Police, has now essentially explained why.

"I think it's very clear that this is a network that we are investigating. As I've said, it [the investigation] continues at pace," he said.

"There's extensive investigations going on and activity taking place across Greater Manchester as we speak."

He added that the level of police activity was "intense".

Earlier Amber Rudd, the Home Secretary, said the suicide bombing had been "more sophisticated" than other attacks.

"It seems likely – possible – that he wasn't doing this on his own," she said.

There have been reports that the suicide bomber, Salman Abedi, was not the bombmaker but acted as a "mule" for others who were behind the attack.

Four other people have been arrested by police investigating the attack. At least one person was detained at a house in Aston Avenue, south Manchester.

Neighbours reported seeing a man in handcuffs on the street along with members of his family, including his wife, an adult son, a teenage daughter and two teenage sons.

There was also a controlled explosion at a flat in Granby Row in central Manchester as police carried out a search of the property.

Soldiers have been ordered onto the streets to protect potential targets such as the Houses of Parliament, Downing Street and New Scotland Yard.

Abedi, 22, who was born in Manchester in 1994 to parents of Libyan birth, had recently returned from Libya, according to Ms Rudd.

French Interior Minister Gerard Collomb told BFMTV that Abedi had been linked to Isis and may have visited Syria.

“Today we only know what British investigators have told us – someone of British nationality, of Libyan origin, who suddenly after a trip to Libya, then probably to Syria, becomes radicalised and decides to carry out this attack,” he said.

Asked if he believed Abedi had the support of a network, Mr Collomb said: “That is not known yet, but perhaps. In any case, (he had) links with Daesh (Isis) that are proven.”

Reuters contributed to this report