Grave new questions were raised over a gaping 'backdoor to Britain' last night following the horrific Belfast knife attack.

The Sudanese suspect legally crossed from the Republic of Ireland to Northern Ireland three years ago under a long-standing arrangement which means no passport checks are conducted.

He took a bus from Dublin to Belfast and immediately claimed asylum, the authorities revealed under pressure for answers yesterday.

A few months later the Home Office granted him a five-year visa as a refugee.

The horrific street stabbing on Monday night left a man in his 40s in a critical condition and prompted calls for a review of border security measures deployed under the so-called Common Travel Area, or CTA, which encompasses the UK, Northern Ireland and the Republic.

Police last night charged the 30-year-old suspect, who will appear in court today. The victim, it is understood, lived in the same block of social housing.

Officers have said they did not believe the attack was related to terrorism.

Protesters gathered on the streets across Belfast long before dark last night following rallying cries on social media, ignoring police pleas for calm.

Just before 8pm, masked men dressed in black pushed burning bins up against a bus, setting it ablaze and sending thick smoke into the sky.

Houses and cars were also later set alight.

Earlier, following repeated questions about the suspect's immigration status, Police Service of Northern Ireland Chief Constable Jon Boutcher confirmed the alleged knifeman had travelled from Sudan to Paris and then on to Dublin, before taking a bus into the UK in February 2023.

Shadow Home Secretary Chris Philp said: 'The CTA means the UK relies on the Republic of Ireland to secure its border, and any weakness in the Irish border is also a weakness in ours.

'Clearly, a lot more must be done to prevent the CTA operating as a backdoor to the UK for illegal immigrants.

'We need a review into border security measures in the interests of the UK and the Republic of Ireland.'

Under the CTA, a key part of the Good Friday Agreement, there are typically no checks on travellers between the Republic and Northern Ireland, nor any on journeys to mainland Britain.

David Wood, the Home Office's director of immigration enforcement until 2015, said: 'The CTA has always been a weakness and on some days we used to find that there were no checks at all being conducted at Dublin airport.

'Anyone arriving in the Republic can be in London, Manchester or wherever they want to be within a day or two.

'The CTA is an abused route and it's always been an abused route.'

A 2010 assessment by the UK's Cross Border Organised Crime Group concluded that 'Ireland can be used as a back door to gain access to the United Kingdom and vice versa'.

The following year a report by then Chief Inspector of Borders and Immigration John Vine urged the Home Office to 'strengthen' measures to prevent abuse of the CTA.

Northern Ireland's Justice Minister, Naomi Long, said yesterday: 'What we don't want on either side of the border is to see the CTA being exploited for ill purposes.'

Home Office sources said there was no record of the suspect being in the UK before 2023.

Horror unfolded at around 10.30pm on Monday night in Kinnaird Avenue, north Belfast, a majority Roman Catholic area.

Graphic video footage filmed by witnesses and shared on social media showed a man armed with a knife pinning another man to the ground before repeatedly striking him to the face and neck.

Before police arrived, the suspect was tackled by brave passers-by, including removals firm boss Matt McKiernan, who used his son's hurling stick to try to stop the attack, hitting the knifeman several times.

Last night he told the Daily Mail: 'We could see what looked to be two men fighting in the street, with one on top of the other.

'We thought we better go and break it up. [My friend] Andre was in the front passenger seat and he jumped out first.

'But as he got closer he saw the knife. He shouted to me… to get something to help.'

The victim remained in hospital on Wednesday, where he was being treated for serious eye, face and back wounds, police said.

The Belfast Telegraph reported that witnesses fear he was blinded in the attack.

The suspect was last night charged with attempted murder, possession of an article with blade or point in a public place and threats to kill.

In Northern Ireland, the authorities do not release the name of accused persons before they appear in court.

In a press conference, Northern Ireland deputy first minister Emma Little-Pengelly called on the British government to address concerns about migrants of unknown status freely entering Northern Ireland across the Irish border.

'We have been aware for some considerable time that there are people coming across the Irish border to claim asylum in Northern Ireland,' she said.

'Those people, very often we do not know their background, we do not know the routes that they come through, and we do not know if they have any convictions or any history in another jurisdiction.'

Nigel Farage, on a visit to Grangemouth in Scotland, said the attack was 'absolutely shocking, barbaric, ghastly'.

The Reform UK leader added: 'He was given leave to remain, as almost all these people are. We dish out leave to remain like Smarties to people about whom we know nothing, and some of whom cause great harm in our country.

'Frankly, these people shouldn't be here.'

Far-Right agitator Tommy Robinson and X owner Elon Musk urged people to take to the streets of Britain and demonstrate.

PSNI assistant chief constable Ryan Henderson warned that disorder 'damages communities, damages local businesses and brings young people into the criminal justice system when they shouldn't be'.