Manchester suicide bomber Salman Abedi's mother told authorities that her son had been radicalised, it has been claimed.

News sources in the US, citing intelligence officials, have said members of Abedi's family had informed on the 22-year-old as they feared he had become 'dangerous'.

Adebi spoke to his nuclear scientist mother, Samia Tabbal, on the phone in Tripoli shortly before he detonated the device on Monday night.

A Libyan security source told the BBC’s Newsnight that Abedi rang his brother in Libya, telling him to get their mother to call him.

Lounging on the beach in Libya with friends and hanging out with his mates in Manchester, this is Salman Abedi (circled) as a teenage boy before he became a suicide bomber. There is a no suggestion any of the friends he is pictured with have been involved in any wrong doing

Abedi's younger brother Hashem (pictured) has also reportedly been arrested in Tripoli, Libya, on suspicion of having links to the ISIS, that claimed responsibility for the atrocity

It also emerged that Tabbal, 50, graduated from Tripoli university 'top of her class'.

A US intelligence official, who claimed to have direct knowledge of the investigation, told NBC that Abedi had ties to al Qaeda and had received terrorist training abroad.

In the last 12 months the terrorist had traveled to Libya and could have connections to several extremist groups.

The news came as Abedi's father, Ramadan, was detained by masked gunmen while recording TV interviews in Libya and his younger brother, Hashem, 20, was arrested in Tripoli on suspicion of having links to the ISIS.

His mother, Samia Tabbal, 50, and father, an airport security officer, were both born in Tripoli but emigrated to London to flee the Gaddafi regime. They moved to the Whalley Range area of south Manchester where they have lived for at least a decade.

UK security services are now facing claims they were warned by the terror attacker's family and friends that he was dangerous.

Two people who knew Salman Abedi are said to have called the police counter-terrorism hotline five years ago to report that he thought 'being a suicide bomber was OK'.

The calls, revealed by a community worker to the BBC, emerged after US intelligence sources suggested Abedi's relatives had also tried to alert the authorities that he was a potential threat.

Ramadan Abedi (pictured) the father of Manchester Arena bomber Salman Abedi claims his son seemed 'normal' when they last spoke five days ago and insists: 'We don't believe in killing innocents'

Salman Abedi (pictured) had only just returned from war-torn Libya before launching his horrific attack and is believed to have undergone secret jihadi training

Home Secretary Amber Rudd admitted today that the 22-year-old was 'known' to the security services 'up to a point'.

Meanwhile, the government is under pressure to toughen up 'shambolic' border checks that mean jihadis returning to Britain from ISIS battlefields are not challenged.

As a picture began to emerge of the 22-year-old behind the atrocity in Manchester, a community worker told the BBC two people who knew Abedi at college had called the counter-terror hotline raising concerns.

RUDD'S FRUSTRATION AT US LEAKS FROM TERROR PROBE Amber Rudd vented her frustration today over US leaks about details of the Manchester terror attacks. The Home Secretary delivered a rare public rebuke to our close allies by admitting she was 'irritated' by the way 'operational' information had been disclosed. She said she had made 'very clear' to the US that such leaks 'cannot happen again'. But the Cabinet minister's warning seems to have fallen on deaf ears - as both American and French officials have been revealing more details about the case. 'The British police have been very clear that they want to control the flow of information in order to protect operational integrity, the element of surprise,' she told BBC Radio 4's Today programme. 'So it is irritating if it gets released from other sources. 'I have been very clear with our friends that it should not happen again.' Advertisement

They are said to have told police around five years ago that the student was 'supporting terrorism' and had expressed the view that 'being a suicide bomber was OK'.

Meanwhile, a US intelligence official told NBC members of Abedi's own family had informed on him in the past.

The official said the bomb he used was so 'big and sophisticated', including materials hard to obtain in Britain, that it was 'almost impossible to see he didn't have help'.

Abedi was apparently identified by a bank card found in his pocket at the scene of the explosion, with his name then confirmed by facial recognition technology.

The latest leaks out of the US will infuriate ministers, who have been trying to keep details of the investigation under wraps.

Troops are being deployed onto Britain's streets today amid fears a further terror attack 'may be imminent'.

Abedi, a Mancunian of Libyan descent, detonated his nail bomb at an Ariana Grande concert at the Manchester Arena on Monday night, killing himself and 22 others.

Ms Rudd said today that Abedi, who is reported to have recently returned to the UK from a visit to Libya, was known to the intelligence services 'up to a point'.

France's interior minister revealed that Abedi is thought to have been in Syria, and had 'proven' links to ISIS.

Abedi is believed to have traveled to Libya within the last 12 months. The US source said while he had 'clear ties to al Qaeda,' there could also have been connections to other groups.

About 850 Britons are thought to have gone abroad to fight with so-called Islamic State as they took control of large swathes of territory in Syria and Iraq.

But with the terror group being pushed out, extremists with British passports are fleeing back to the UK where authorities fear they may unleash a new wave of attacks.

Although more than 100 have been killed, around half have returned home with battle experience and training in the use of explosives and firearms.

The numbers of extremists are stretching the UK's security services to breaking point, with up to 30 officers required to provide 24-hour monitoring of just one suspect. Restricted resources mean MI5 can watch around 50 terror suspects around the clock at any given time.

This photo shows the aftermath of the suicide bomb which ripped through the foyer of the venue killing parents and children

Ukip spokesman Patrick O'Flynn said the weak border controls left Britain 'wide open' to the terror attack

Khalid Mahmood, who is defending the Birmingham Perry Bar seat for Labour at the election, told MailOnline the case of Abedi demonstrated the weakness of the system.

'I am extremely concerned that this is another case where a returning fighter has come straight through our border checkpoints,' he said.

'I am not making it an issue of the election, I am making it an issue of security.

Mr Mahmood said border staff had been reduced by 50 per cent since 2010.

'We don't have and have never had secure borders,' he said. 'This is an individual who has come back with devastating effect.

HOW SECURITY SERVICES HANDLE RETURNING FIGHTERS When foreign fighters are detected returning to Britain, security services assess whether they have genuinely repudiated ISIS or remain a hardline fanatic. Where there is clear evidence against the individual in question, they can be prosecuted in the UK. Foreign nationals can be prevented from coming back into the country, and duel nationals can be stripped of British citizenship. For UK citizens, there are temporary exclusion orders, which make it unlawful for the subject to return unless they agree to conditions. Terrorism Prevention and Investigation Measures (Tpims) can be imposed, involving restrictions including relocation and electronic monitoring. In addition to those returning from jihad, MI5 and police must also deal with the issue of people who have been blocked from going to conflict zones. Around 150 attempted journeys to Iraq and Syria were thwarted in 2015. Advertisement

Mr Mahmood said the abscence of checks meant security services had to 'work 10 times harder to try and catch up with these people once they have come back'.

He said there was too much reliance on biometric passports, with the main focus on monitoring people's immigration status.

'You just walk through,' he said. 'It doesn't check how long you have been out and where you have been to,' he said.

'We cannot protect our borders by digital means alone.

'I find it absolutely absurd that this happened again. It was bound to happen.

He added: 'Everywhere else you go there is a full inspection of who is going in and out. At least it gives you some sort of protection...

'We have not got a clue of what is going in and going out.

'How can we give a number (for how many jihadis have returned to the UK)? We have no idea.'

Mr Mahmood said Mrs May had to 'take responsibility' for the border 'shambles' because she was Home Secretary for six years.

Former security minister Lord West added his voice to calls for more rigorous passport checks on arrival and departure from the UK.

'I think there is no doubt our security situation has got significantly better since 7/7,' he told MailOnline.

'But what happened is the Arab Spring. That overturned everything in the Middle East.

'The threat has got worse and worse again.

'As our military are more successful in Iraq and finally in Syria, Daesh will not have a caliphate... people including from Britain will go their way very highly radicalised with knowledge of weapons.'

He added: 'I do think checking of passports could be tightened up a lot. I think we should check them as people leave.'