Just before 2:40pm in London, police officers, doctors, and faith leaders marched across Westminster Bridge holding banners that read "love for all, hatred for none".
The sombre atmosphere marked exactly one week since an attack that shook Britain to its core.
One of the march's organisers, Police Sergeant Jim Southgate, says it symbolised a show of strength as well as support.
"We're going to stand up to terrorism, we're not going to take this lying down. Yes, we will pick ourselves back up and the fact is we will be there for the victims."
Mustafa Field, from the Faiths Forum for London, says he was heartened to see Jewish, Christian and Muslim groups come together for the event.
"We've seen a real interest, a desire, from the different faith traditions across London to come together, to hold hands, to stand on the bridge where the attack took place to pay respects."
As the vigil reached Parliament, dozens of people laid flowers at the side of the bridge, including family members of those killed or injured.
Reverend Femi Cole-Njji runs a church in east London.
She says it's important for all Londoners to support those who've been affected.
"We are standing in solidarity with families who have lost loved ones, but mostly to show the world that we are one irrespective of what faith we represent. We've come together to stand together with the families and to demonstrate serenity, which is just so important in our world today."
Events were also held in Leeds, Manchester, Birmingham and other cities.
The Duke of Cambridge, Prince William, laid a wreath at the National Memorial Arboretum in Staffordshire.
Earlier, inquests into the victims' deaths were opened and adjourned at Westminster Coroner's Court.
The court heard that the attacker, Khalid Masood, had driven his vehicle up on to the pavement twice while crossing Westminster Bridge, in an apparently deliberate attempt to target pedestrians.
He killed three people: teacher and mother of two Aysha Frade, US tourist Kurt Cochran, and a 75 year old retired window cleaner, Leslie Rhodes.
Masood then crashed the car into the east perimeter railings of the Palace of Westminster.
Armed with two knives and wearing a stab vest, Masood fatally stabbed police officer Keith Palmer before being shot dead himself.
During a ceremony at New Scotland Yard, the Acting Commissioner of London's Metropolitan Police, Craig Mackey, led tributes for PC Palmer's sacrifice.
"This afternoon is about remembering the victims of last week's events. Our thoughts, our prayers, go out to everyone who was affected by the events last week. I would urge you, if you get time, to go onto the bridge, talk to Londoners - talk and get a feel for this great city and how it's come together in responding to these events."
A full police funeral service will be held for PC Palmer on April 10, followed by a private cremation.
British MPs have announced two reviews of the attack will be held, including a report on the "lessons learned" from the response, which will be released in June.
An inquest into Khalid Masood's death will also be opened and adjourned later on Thursday.
