The Islamic State terror group has claimed responsibility for the Manchester suicide bombing which killed 22 victims, including an eight-year-old girl, in the worst terrorist incident to hit Britain since the July 7 attacks.

A lone bomber detonated a homemade device packed with nuts and bolts in the foyer of the Manchester Arena as thousands of young people were leaving a concert by US pop star Ariana Grande on Monday night.

The attacker has not been officially named but investigators believe they know his identity.

On Tuesday, the first arrest was made in connection with the inquiry.

Greater Manchester Police said in a statement: “With regards to the ongoing investigation into last night’s horrific attack at the Manchester Arena, we can confirm we have arrested a 23-year-old man in south Manchester.”

One witness told how the man was detained by between six and eight plain-clothes officers in Chorlton.

Speaking outside Downing Street after chairing a meeting of the Government’s Cobra emergency committee, Mrs May said the perpetrator had chosen the time and place of his attack deliberately to cause “maximum carnage and to kill and injure indiscriminately”.

Mrs May, who later flew to Manchester to speak to police chiefs, paid tribute to emergency workers and members of the public who rushed to help.

The PM said: “It is now beyond doubt that the people of Manchester and of this country have fallen victim to a callous terrorist attack, an attack that targeted some of the youngest people in our society with cold calculation.

“This was among the worst terrorist incidents we have ever experienced in the United Kingdom, and, although it was not the first time Manchester has suffered in this way, it is the worst attack the city has experienced and the worst ever to hit the north of England.”

Manchester Arena blast. Detailed maps of the area graphic
(PA graphic)

She said: “We now know that a single terrorist detonated his improvised explosive device near one of the exits of the venue, deliberately choosing the time and place to cause maximum carnage and to kill and injure indiscriminately.”

The Prime Minister said: “All acts of terrorism are cowardly attacks on innocent people, but this attack stands out for its appalling, sickening cowardice, deliberately targeting innocent defenceless children and young people who should have been enjoying one of the most memorable nights of their lives.”

Mrs May said there would be “difficult days ahead” for those affected, but added: “We all – every single one of us – stand with the people of Manchester at this terrible time.

“And today, let us remember those who died and celebrate those who helped, safe in the knowledge that the terrorists will never win and our values, our country and our way of life will always prevail.”

The Prime Minister said the official threat level remains at severe – meaning an attack is highly likely – but this would be assessed throughout the day.

Police were called to reports of an explosion at the Manchester Arena at 10.33pm on Monday, shortly after the end of the performance.

The massive blast sparked panic as concert-goers rushed to exit the venue, which has a capacity of 21,000.