Seven people are dead and at least 48 people are injured following a terror attack in central London last night.
A van was driven into pedestrians on London Bridge before moving to Borough Market where three suspects got out and stabbed people.
People socialising in local pubs were told by police to get on the floor while officers hunted down the attackers.
The men - who were wearing fake explosive vests - were shot dead by police.
The British Prime Minister has offered her "huge gratitude" to the emergency services - and says her thoughts are with those caught up in what happened.
Theresa May will be holding a meeting of the UK's emergency response committtee COBRA to discuss the situation.
Metropolitan Police Assistant Commissioner Mark Rowley outlined the chain of events:
The Taoiseach Enda Kenny is among the world leaders expressing their shock at the attack.
Mr Kenny tweeted last night: "Terrible news coming from London - we stand with our close neighbours again tonight."
Terrible news coming from London - we stand with our close neighbours again tonight. @IrelandEmbGB monitoring the situation.
— Enda Kenny (@EndaKennyTD) June 3, 2017
French President Emanuel Macron said France was "more than ever at Britain's side" after the attacks.
US President Donald Trump has offered his condolences - saying America is ready to help.
Whatever the United States can do to help out in London and the U. K., we will be there - WE ARE WITH YOU. GOD BLESS!
— Donald J. Trump (@realDonaldTrump) June 3, 2017
The city's mayor Sadiq Khan has described it as "deliberate and cowardly".
