THREE men have been arrested in connection with the Manchester concert suicide bombing as a huge investigation into the attack gathers pace.

They were detained after police executed warrants in the south of the city, taking the total of people in custody to four.

Officers were also carrying out a search at an address in Manchester city centre as part of the inquiry into the atrocity.

Across the country there have been vigils to the 22 people who were killed, which included Georgina Callander and Saffie Rose Roussos from Lancashire.

Dozens were more seriously injured when Salman Abedi detonated a device as fans left Manchester Arena, where US star Ariana Grande was performing on Monday night.

It was the worst terrorist incident to hit the UK since the July 7 attacks in London in 2005.

With Britain on high alert for further attacks as investigators worked to establish whether Abedi was part of a wider cell:

France's interior minister disclosed that Abedi, 22, is believed to have travelled to Syria and claimed he had "proven" links with Islamic State;

 Home Secretary Amber Rudd confirmed the attacker was known to intelligence services "up to a point";

 Almost 1,000 military personnel were being deployed around the country, including to key sites such as Parliament, Buckingham Palace and Downing Street, after the official terror threat assessment was raised to critical, the highest level, indicating that a further attack may be imminent;

Police said they are "confident" they know the identity of all the people who died in the bombing, but they will not be formally named until forensic post-mortems are completed in four to five days.

As the investigation continued, neighbours said a Libyan father, his wife and their two sons, aged in their late teens or early 20s, were taken away by armed police who raided a property on Aston Avenue, Fallowfield, at around 2.30am on Wednesday.

The house is less than a mile from the former home of Abedi.

Neighbour Omar Alfakhuri said at least six police vehicles arrived and armed police took the family out one by one, wearing their bedclothes.

Mr Alfakhuri said the family had lived at the address for 15 years and described the father as religious who prayed at a local mosque.

There was also a raid at a block of flats close to Manchester Piccadilly Station in the city centre.

Prime Minister Theresa May announced late on Tuesday that the terrorism threat level was being raised to "critical" - the highest alert level - meaning that an attack is thought be imminent.

It is the first time the most serious rating has been reached for nearly a decade.

The move reflects fears that a "wider group of individuals" may have been involved in the attack - including the bomb-maker who provided Abedi with his deadly device.

Meanwhile, Mr Mike Wright, Headteacher of St Augustine’s said “We received news that one of our year 7 pupils, Emily Murrell (12), and her mother sustained injuries caused by the explosion at the MEN Arena on Monday night and underwent surgery at Manchester MRI and Manchester Children’s Hospital.

"Both Emily and her mother are in the recovery units of the hospitals and medical professionals are pleased with the progress they are making as they await further treatment.

"Our thoughts and prayers are with the family at this most distressing time.”