olice raid several addresses in east London suburb of Barking after attack at London Bridge left seven dead.
Police have arrested 12 suspects linked to Saturday night's attack in central London, the Metropolitan Police said.
Counterterrorism police raided several addresses in the east London suburb of Barking on Sunday, the force said, adding that searches were continuing there.
Four women were seen being led away by police by an AFP photographer, although it was not clear whether they were among those arrested.
At least seven people died and dozens were injured after attackers drove a van into pedestrians on London Bridge before stabbing people at bars and restaurants in nearby Borough Market on Saturday night.
The attack ended after police shot dead three suspected attackers.
Metropolitan Police Commissioner Cressida Dick earlier told reporters that she believed the imminent threat from attackers had been ended, but that a fast-moving investigation was still under way.
"We have a very large investigation ongoing, and we will be seeking to establish whether anyone else was working with or assisting in any way or helping in the planning of this attack," she said.
London Bridge is a major transport hub and nearby Borough Market is a fashionable warren of alleyways leavened with bars and restaurants that is always bustling on a Saturday night.
The area remained cordoned off and patrolled by armed police and counterterrorism officers on Sunday, with train stations closed.
The attack occurred five days ahead of a parliamentary election and was the third to hit Britain in less than three months. Prime Minister Theresa May said the election would go ahead as planned on Thursday.
"It is time to say enough is enough," said May in a televised statement outside her Downing Street office, where flags flew at half-mast.
"We cannot and must not pretend that things can continue as they are," May said, calling for a strengthened counter-terrorism strategy that could include longer jail sentences for some offences and new cyberspace regulations.
Al Jazeera's Jonah Hull, reporting from London, said that repeated attacks like this have a huge impact and were deeply unsettling and worrying.
"But life does go on - this is an enormous city and from Monday I've no doubt that people will begin to go about their business as they probably are already," said Hull. "They are used now to seeing higher police presence on the streets."
Thirty-six people injured in the attack remain in hospital and 21 are in a critical condition, said Metropolitan Police Assistant Commissioner Mark Rowley in a statement on Sunday.
Rowley also said a member of the public had suffered a gunshot wound as officers fired on the attackers. The individual is being treated in hospital and is not in a critical condition, Rowley said.
Eight armed officers opened fire as they attempted to stop the knife-wielding attackers and discharged around 50 bullets, he said.
Two French nationals were among those injured in the London attack, the French president's office said in a statement. Australia said two of its citizens were caught up in the attack and that one was in hospital.
The suspects were wearing what appeared to be suicide vests, but police said they were later established to be fake.
There was no immediate claim of responsibility.
The Islamic State of Iraq and Syria (ISIL, also known as ISIS), losing territory in Syria and Iraq to an advance backed by a US-led coalition, had sent out a call on instant messaging service Telegram early on Saturday urging its followers to carry out attacks with trucks, knives and guns against "Crusaders" during the Muslim holy month of Ramadan.
London Mayor Sadiq Khan described the incidents as a "deliberate and cowardly attack on innocent Londoners".
Harun Khan, Secretary General of the Muslim Council of Britain, said in a statement on Sunday: "Muslims everywhere are outraged and disgusted at these cowards who once again have destroyed the lives of our fellow Britons. That this should happen in this month of Ramadan, when many Muslims were praying and fasting only goes to show that these people respect neither life nor faith."
"Another witness said three men got out with long blades and randomly started stabbing people along Borough High Street. Other witnesses have also mentioned seeing knife victims," he said.
Police ruled a third incident - a stabbing in London's Vauxhall area initially thought to be linked to the other two scenes - to be unrelated.
The attack came days ahead of a June 8 general election, almost two weeks after 22 people were killed in a bombing at a concert in Manchester.
After that attack, Britain's official threat level was raised to "critical", meaning an attack may be imminent. Several days later it was lowered to "severe", meaning an attack is highly likely.
In March, an attacker ran people down with a vehicle on Westminster Bridge, killing four before stabbing a policeman to death outside Parliament.
World leaders quickly took to social media to offer their support to the people of London.
"Faced with this new tragedy, France is now more than ever supporting the UK. My thoughts are with the victims and their loved ones," tweeted French President Emmanuel Macron.
Australia's foreign minister described the incidents as a "shocking".
US President Donald Trump also tweeted in connection with the London attacks: “We are with you. God Bless”.
He pledged support for the UK, but also used attacks to argue in favour of his controversial travel ban.
Sources : aljazeera
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