At least seven have been killed in the third attack to hit the UK since March. As in those earlier incidents, jihadi sympathisers online lauded the violence before ISIS claimed it.
This briefing will be updated as events develop
At least seven people were killed on Saturday night, and 48 people injured, when a white van rammed into pedestrians on London Bridge. Three men wielding large knives then got out of the vehicle in nearby Borough Market and attacked passersby, entering at least one eatery in the popular restaurant and bar area.
ISIS claimed responsibility on Sunday evening, 24 hours after the attack took place, via its affiliated Amaq news agency. The statement described the perpetrators as "a detachment of fighters of the Islamic State," but provided no further details about their identities or the incident.
There was some confusion around the claim, with the initial statement carrying the wrong date. A correction was published shortly afterwards. The statement did not add to existing media coverage of the attack, indicating tenuous links at best. The violence may have been inspired by the extremist group, rather than directly coordinated, following the trend of earlier attacks in the UK this year.
The three assailants were named later in the week. Khuram Butt, 27, was known to police and had appeared in a Channel 4 documentary, "The Jihadi Next Door." The Pakistani-born man, who grew up in the UK, had previously been reported to the UK's anti-terror hotline. Butt had links to al-Muhajiroun, a banned extremist group led by hate preacher Anjem Choudary, who was jailed last year for supporting ISIS. While police were aware of Butt's case, they did not suspect he was planning an attack and he was subsequently moved to the "lower echelons" of investigation, security forces said. The second named perpetrator, Rachid Redouane, who claimed both Moroccan and Libyan heritage, was not known to police. The third was Youssef Zaghba, a 22-year-old Moroccan-born Italian, who was flagged on an international terrorism database after he was stopped while trying to travel to Syria.
Saturday night's incident followed two deadly ISIS-claimed attacks in London's Westminster and Manchester in March and May. The Westminster assault, in which six including the perpetrator were killed, also involved vehicle ramming and stabbing. As with those earlier incidents, ISIS sympathisers online quickly celebrated the violence, publishing warnings and images, before the claim.
Police shot and killed the three attackers within eight minutes of the first call coming in to emergency services on Saturday night. They were wearing 'hoax' suicide vests, according to authorities. At least two eyewitness claimed the perpetrators shouted "this is for Allah."
Police are investigating whether the assailants were working alone. The fact that three men were involved indicates a certain level of planning, although there has been no information so far on whether they had ties to a broader terrorist network. Prime Minister Theresa May said on Sunday morning that police had intercepted five plots since March, and that though the three recent incidents were not connected by "common networks," they shared "Islamist extremist ideology... a perversion of Islam and a perversion of the truth." Most political parties suspended campaigning ahead of the UK general election on 8 June. Twelve people were being held by police after early morning raids in London in connection with the attack but one 55-year-old man was released. On Monday morning, police raided two more addresses in East London and detained a number of people.
In ISIS' claim of the IED blast at an Ariana Grande concert in May, in which 22 people, including children, were killed, the jihadi group warned that "what comes next will be more severe on the worshippers of the Cross and their allies."
According to terrorism researcher Rita Katz, earlier on Saturday a pro-ISIS channel had published a call to 'lone wolves' to carry out attacks in the West during the Muslim Holy month of Ramadan, which started last week. "Kill the civilians of the Crusaders, run over them by vehicles," a post said, with an image of a white van, knife, and gun. In ISIS' claim of the Manchester attack the group also referred to the victims as "crusaders."
ISIS' official magazine, Rumiyah, has instructed readers to carry out lone attacks on the West, with directives on new tactics for carrying them out in its most recent issue.
Al-Qaeda has also made the same appeal. Last month, a propaganda video featuring Osama bin Laden's son Hamza centered around "advice for martyrdom-seekers in the West," in which he urged extremists to carry out attacks in the West. In 2010, al-Qaeda's Yemeni branch (AQAP) ran an article in its English-language magazine calling the pick-up truck a "mowing machine... to mow down the enemies of Allah." Although ISIS has taken responsibility for recent terrorist attacks in Western countries, it is important not to discount the global appeal that al-Qaeda maintains.
Aside from Manchester, recent ISIS-claimed attacks in places like London, Berlin, and Nice have been low-tech, using vehicles and knives, tactics that evade authorities and allow militants who are unable to plan larger attacks to participate in terrorism.
Jihadi ideologues associated with both al-Qaeda and ISIS have long encouraged attacks on soft targets such as the popular nightspot at Borough Market. As a second order effect, the clamping down on individual freedoms in the name of security is touted as a form of victory for such groups. ISIS has at times justified violence against civilians for their role in electing politicians who carrying out strikes on their so-called 'caliphate,' framing such deaths as collateral damage, something used by other jihadi ideologues in justification of violence.
Some assaults have been framed as being against the perceived decadence and un-Islamic practice of the West. ISIS' official claim of responsibility for the November 2015 Paris attacks described the Bataclan concert venue, where 89 people were killed, as a den of "prostitution and vice." After the Paris attacks, Mark Rowley, head of counter-terrorism for the Metropolitan Police, warned, "In recent months we've seen [many] more plans to attack Western lifestyle, going from that narrow focus on police and military as symbols of the state to something much broader."
Theresa May raised the UK terror threat to "severe" in August 2014 and following the naming of the suspect in May's Manchester attack, increased it to "critical," the highest level. It has since been reduced to "severe."
The Director General of MI5, Andrew Parker, has said that there would be successful attacks in the UK at some stage, and more recently the top counter-terror official at the EU claimed that attackers would be more dangerous as an exodus of increasingly seasoned fighters return from the failing ISIS operations in the Middle East.
The extremist threat throughout Europe is still severe. Between March and December 2016 there were at least 320 extremist arrests in 16 countries throughout the continent. Last year, there were at least two other Islamist attacks in Britain. In March 2016, an individual from Bradford travelled to Glasgow to murder an Ahmadi shopkeeper for supposed blasphemy. In February 2016, a Sufi leader was murdered by two ISIS supporters for supposedly practicing black magic.