Twelve people have been arrested after the London terror attack which left seven people dead and 48 injured.
The arrests in Barking, east London, followed a raid at a flat belonging to one of the three attackers.
A van hit pedestrians on London Bridge at about 22:00 BST on Saturday. Three men then got out and stabbed people in nearby Borough Market; the attackers were shot dead by police minutes later.
Condemning the attack, Theresa May said it was “time to say enough is enough”.
Twenty-one people injured in the attack are in a critical condition, NHS England has said.
Controlled explosions were carried out at the flat in Barking during the raids on Sunday morning.
According to neighbours, the dead attacker lived there for about three years and was married with two children.
It is the third terror attack in the UK in three months, following the car and knife attack in Westminster in March, in which five people were killed, and the Manchester bombing less than two weeks ago, in which 22 people were killed.
Most political parties have suspended national general election campaigning, but the prime minister said full campaigning would resume on Monday. The general election will go ahead as planned on Thursday.
Eyewitnesses to the attack described a van travelling at high speed along London Bridge, hitting pedestrians, before crashing close to the Barrowboy and Banker pub. Three men then got out wearing fake bomb vests and began attacking people in the nearby market – an area known for its bars and restaurants, which were busy on a warm summer evening.
Four police officers who tried to stop the attack were among those injured, two of them seriously.
One of them was an off-duty officer and amateur rugby player who tackled one of the terrorists, suffering stab wounds.
Another, a British Transport Police officer who joined the force less than two years ago, took on the attackers armed with only his baton.
Metropolitan Police Commissioner Cressida Dick praised their “extraordinary bravery”.
The three suspects were shot dead within eight minutes of the first 999 call being received.
Among the main developments:
More than 80 medics were sent to the scene. The injured, some of them in critical condition, are being treated in five London hospitals
The Met Police has set up a casualty bureau on 0800 096 1233 and 020 7158 0197 for people concerned about friends or relatives
A Canadian national was among those killed, the country’s Prime Minister Justin Trudeau said
Two Australian citizens “have been directly impacted,” says the country’s Prime Minister Malcolm Turnbull
Four French citizens have been injured, one seriously, according to foreign minister Jean-Yves Le Drian
There will be a minute’s silence on Tuesday at 11:00 BST in remembrance of those who lost their lives and all others affected by the attacks, Downing Street has said
Prime Minister Theresa May has made a private visit to King’s College Hospital in south London to visit the injured
Speaking in Downing Street after a meeting of the government’s emergency Cobra committee, the prime minister said the country “cannot and must not pretend that things can continue as they are”. “We believe we are experiencing a new trend in the threat we face as terrorism breeds terrorism,” she said.
Mrs May said the counter-terrorism strategy would be reviewed and the UK would work with other countries to prevent the internet being a “safe space” for terrorists. She said there was “too much tolerance of extremism in our country” and while it would involve “some difficult and embarrassing conversations”, that must change.
The country’s terror level remains at severe – meaning an attack is highly likely – but has not been raised to critical as it was after the Manchester Arena bombing.
Home Secretary Amber Rudd said: “We’re staying at severe because we think they have got all the main perpetrators.”
All through the night supporters of so-called Islamic State have been celebrating the London attack, even before any claim has been made by IS. There was never much doubt either in their minds, or in those of British counter-terrorism officials, that this was a jihadist attack inspired by IS.
It follows a widely-circulated propaganda message put out by the group on social media urging its followers to attack civilians in the West using trucks, knives or guns.
The message makes reference to the current Islamic holy month of Ramadan. Last year attacks intensified during this month with deaths resulting in Istanbul, Dhaka and Baghdad. Some analysts see this as a last desperate bid by IS to its supporters, following multiple setbacks in the Middle East where its self-proclaimed caliphate is shrinking fast. However, the ideology of IS is likely to survive those defeats and will continue to fuel terrorist attacks around the world.
London Mayor Sadiq Khan said the capital remained the “safest global city” and would not be cowed by terrorism.
Harun Khan, secretary general of the Muslim Council of Britain, said Muslims everywhere were “outraged and disgusted at these cowards who once again have destroyed the lives of our fellow Britons”. He added: “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.”