London (CNN) British police have identified two of the three men behind Saturday night's terror attack in London as Khuram Shazad Butt and Rachid Redouane.

Updates: Two men shot dead by police following terrorist attack in #LondonBridge #BoroughMarket named https://t.co/prQUaxy2k4 pic.twitter.com/LR4klVhZ64

Butt, 27, was a British citizen who was born in Pakistan, London's Metropolitan Police said. Police and MI5, the UK's counterintelligence and security agency, were familiar with him, but there was no intelligence to suggest the weekend attack was being planned, police said.

Butt briefly worked for Transport for London, the entity that oversees the city's public transport system. He was a trainee customer services assistant with London Underground for less than six months, before leaving in October, a Transport for London spokesperson said.

Redouane, 30, who also used the name Rachid Elkhdar, had claimed to be Moroccan and Libyan.

The third attacker has been identified, police said, but his name has not been publicly released.

The assailants killed seven people and wounded 48 others by ramming a vehicle into a crowd on London Bridge and then stabbing people in nearby Borough Market.

Photos: London Bridge, nearby cafe target of terror attack Forensic officers work at the scene of a terror attack at London Bridge in London on Sunday, June 4. At least seven people were killed in attacks late Saturday as a van mowed down pedestrians on London Bridge before attackers then stabbed victims at nearby Borough Market. Hide Caption 1 of 26 Photos: London Bridge, nearby cafe target of terror attack Counterterrorism officers patrol near the scene of the attack on London Bridge. When speaking to the media on Sunday, British Prime Minister Theresa May did not announce any increase in the UK terror threat level. Hide Caption 2 of 26 Photos: London Bridge, nearby cafe target of terror attack A woman reacts after asking a Police officer to lay flowers near London Bridge as a tribute to the victims of the attack. Hide Caption 3 of 26 Photos: London Bridge, nearby cafe target of terror attack UK police officers on Sunday continue their investigation into the terror attacks on London Bridge and in a nearby restaurant district. The attacks on June 3 came days before a general election and two weeks after 22 people were killed when a suicide bomber targeted an Ariana Grande concert in Manchester. Hide Caption 4 of 26 Photos: London Bridge, nearby cafe target of terror attack Prime Minister Theresa May makes a statement at 10 Downing Street, following a Cobra security meeting in response to Saturday night's terror attack. Violence must "never be allowed to disrupt the democratic process," May said, adding that Thursday's general election will go ahead. Hide Caption 5 of 26 Photos: London Bridge, nearby cafe target of terror attack Abandoned buses line London Bridge as the scene remains under investigation following the attack. Metropolitan Police Assistant Commissioner Mark Rowley said in a statement Sunday that a white van struck pedestrians on London Bridge. Attackers then left the vehicle and "a number of people were stabbed, including an on-duty British Transport Police officer who was responding to the incident at London Bridge," said Rowley. The officer received serious but not life-threatening injuries. Hide Caption 6 of 26 Photos: London Bridge, nearby cafe target of terror attack Counter terrorism officers move up an escalator under The Shard, an iconic highrise near the scene of last night's London Bridge attack. Hide Caption 7 of 26 Photos: London Bridge, nearby cafe target of terror attack A group of police forensic officers walks in the street outside Borough Market. Hide Caption 8 of 26 Photos: London Bridge, nearby cafe target of terror attack People lie on the ground after being detained by police at Elizabeth Fry apartments in Barking, east London, which officers raided Sunday, June 4, following Saturday's terror attack at London Bridge and Borough Market. Hide Caption 9 of 26 Photos: London Bridge, nearby cafe target of terror attack A bouquet of flowers left near the police cordon at London Bridge on June 4. Hide Caption 10 of 26 Photos: London Bridge, nearby cafe target of terror attack A view from above shows where a van struck pedestrians on London Bridge -- and then crashed into a barrier. Hide Caption 11 of 26 Photos: London Bridge, nearby cafe target of terror attack This image, from London's Borough Market, shows two of the attackers after they were shot by London police. The attackers drove a white van into pedestrians on London Bridge, leaving bodies lying in the roadway, a witness to the incident told CNN Hide Caption 12 of 26 Photos: London Bridge, nearby cafe target of terror attack Armed police patrol near London Bridge on Saturday, June 3. Mayor Sadiq Khan said it was a "deliberate and cowardly attack" on Londoners enjoying Saturday night out. Hide Caption 13 of 26 Photos: London Bridge, nearby cafe target of terror attack The white van used in the attack is seen near London Bridge. Hide Caption 14 of 26 Photos: London Bridge, nearby cafe target of terror attack Police carry out a search near empty buses on London Bridge, Saturday, June 3. Hide Caption 15 of 26 Photos: London Bridge, nearby cafe target of terror attack A person is treated for injuries near London Bridge. Hide Caption 16 of 26 Photos: London Bridge, nearby cafe target of terror attack Members of the public flee after reports of the incident involving a vehicle and pedestrians. Hide Caption 17 of 26 Photos: London Bridge, nearby cafe target of terror attack Police and emergency responders attend to an injured person. Hide Caption 18 of 26 Photos: London Bridge, nearby cafe target of terror attack An armed Police officer gestures after the attack in central London. Hide Caption 19 of 26 Photos: London Bridge, nearby cafe target of terror attack Guests from the Premier Inn Bankside Hotel are evacuated following the attacks. Hide Caption 20 of 26 Photos: London Bridge, nearby cafe target of terror attack A woman wearing an emergency blanket talks on her phone at London Bridge train station. London Bridge Tube station was closed and London Bridge was closed in both directions. Hide Caption 21 of 26 Photos: London Bridge, nearby cafe target of terror attack Armed police raid The Blue Eyed Maid on Borough High Street. Hide Caption 22 of 26 Photos: London Bridge, nearby cafe target of terror attack Debris and abandoned cars remain at the scene of one of the incidents. Hide Caption 23 of 26 Photos: London Bridge, nearby cafe target of terror attack Police sniffer dogs are seen at London Bridge. Hide Caption 24 of 26 Photos: London Bridge, nearby cafe target of terror attack A helicopter flies near London Bridge. Hide Caption 25 of 26 Photos: London Bridge, nearby cafe target of terror attack People are led to safety on Southwark Bridge, away from London Bridge. Hide Caption 26 of 26

Police shot and killed all three attackers, who were wearing suicide belts that turned out to be fakes.

Twelve people were arrested after the attack. On Monday, Met Police said all those arrested had been released without charges.

Latest developments

-- One attacker had a connection to Ireland, a source briefed by an Irish counterterrorism official said.

-- British Prime Minister Theresa May faced questions over cutting 20,000 police posts in her time as Home Secretary.

-- Britain's most senior police officer Cressida Dick said police resourcing needed to be revised.

-- Leader of the main opposition Labour Party, Jeremy Corbyn, called on for the Prime Minister to resign over cuts.

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British Prime Minister Theresa May faced a barrage of questions Monday on deep cuts made to police numbers in the UK while she was Home Secretary.

Authorities also faced scrutiny over what they knew about the alleged perpetrators of the attack.

The carnage is the third such terror attack on British soil in three months and the second in London involving the use of vehicles as weapons.

In March, 52-year-old British national Khalid Masood rammed a vehicle into a crowd on Westminster Bridge and stabbed a police officer, in an attack that left five people dead.

Counterterrorism officers on Sunday near the scene of the attack.

Police said there would be "increased physical measures on London's bridges to keep the public safe." On Monday, concrete barricades had been erected to separate pedestrians from vehicles on some of the city's major bridges.

May under fire over police cuts

Security had already become a battleground issue ahead of Thursday's general election since a Manchester bombing last month, in which 22 people were killed as they left an Ariana Grande concert.

Pressure on May intensified Monday, when at a campaign event she faced a volley of journalists' questions over police cuts. May said her record was sound, saying she had introduced a raft of anti-terror legislation as Home Secretary. She also said that funding for counterterrorism efforts had been protected.

Metropolitan Police Commissioner Cressida Dick said Monday that the country needed to rethink police resourcing and strategy.

But May defended her government's stance on the issue, saying that her Conservative government had protected police budgets.

"The commissioner of the Metropolitan Police has said the Met is well resourced, and they are, and that they have very powerful counterterrorism capabilities, and they do. We have protected counterterrorism policing budgets. We have also provided funding for the increase of the number of armed police officers," she said at a campaign event.

Jeremy Corbyn, leader of the main opposition Labour Party, called on May to resign over the issue, saying earlier that "you cannot protect the public on the cheap," and promising to recruit another 10,000 police officers if he is elected into power.

Commuters walk across London Bridge on Monday after it partially reopened.

Victim identified

London terror attack victim Chrissy Archibald.

Another 36 men and women are hospitalized, 18 of whom are in a critical condition, according to NHS England.

A memorial was held Monday evening in the capital's Potters Field Park, as the city continues to digest its second attack in two months.

London Mayor Sadiq Khan said Monday the actions of the attackers were perverse and poisonous, adding that they had no place in Islam.

"The acts of these three men on Saturday night was cowardly, was evil and I'm angry and furious that these three men are using to justify their actions the faith that I belong to," he said.

On Sunday night,, ISIS claimed responsibility for the attack, although the group provided no evidence for its involvement or details of the attack.

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Attacker was once asked to leave East London mosque

Butt "infrequently" attended Jabir bin Zayd Islamic Centre in Barking, that mosque said. "We did not know him well, his name was not known to us. It has been brought to our attention that some years ago after interrupting a Friday sermon he was asked to leave the mosque," the statement said.

Butt, who also used the name Abdul Zaitun, is believed to have associated with the outlawed radical Islamist group al-Muhajiroun, co-founded by notorious hate preacher Anjem Choudary . Al-Muhajiroun has been linked to Michael Adebolajo, one of the men convicted of slaying British soldier Lee Rigby near a military barracks in southeast London in 2013.

Mohammed Shafiq, chief executive of the Ramadhan Foundation, said Butt verbally assaulted him the day after Rigby's death.

"Butt called me a 'Murtad,' which means traitor in Arabic, and accused me of being a government stooge when I confronted Anjem (Choudary) about him supporting terrorism and my public campaign against Lee Rigby's murder," Shafiq said in a statement Monday.

Shafiq said police arrived, and Choudary, Butt and two other men were escorted away.

"It is clear that Anjem (Choudary) and his band of terrorist sympathizers were known to the police for many years," Shafiq said.

He added: "I am not surprised that Khuram Butt carried out the terrorist attack and there are serious questions for the authorities."

Neighbor saw attacker teaching children to pray

Police said they seized a huge amount of forensic material in two early morning raids in east London on Monday, as part of their efforts to determine if the three men who carried out Saturday's attack were part of a wider network.

Armed police stand guard in front of floral tributes on Southwark Street near the scene of the attack.

Details of the investigation had been kept closely under wraps, in stark contrast to last month's Manchester bombing, when photos and information from the investigation were repeatedly leaked to the US media , triggering a row between the British and American governments.

Monday's early morning raids follow raids on a housing complex in Barking east London on Sunday, where a series of arrests were made.

CNN's Melissa Bell spoke to residents there who recognized a familiar face among the three dead attackers, identifying him as one of their neighbors and describing him as a family man who kept to himself.

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Barking resident Erica Gasperri said she went to the police after she saw a man, believed to be the attacker, teaching the local children about Islam.

"All of a sudden we saw this individual speaking to the kids ... showing them how to pray," she said. "I could see them from my window."