Theresa May has announced Britain's security measures are being reviewed following the attack in Nice.

As armed police stood guard at the French Embassy in London, Mrs May said the nation "must redouble our efforts to defeat these brutal murderers who want to destroy our way of life".

"The threat level here in the United Kingdom is already at severe - that means that a terrorist attack is highly likely," she said.

"Senior officials today will be reviewing what more we can do to ascertain whether there is any further action to take.

"Our security services and our police are ever vigilant."


She said the capital stands "shoulder-to-shoulder" with France as it has done in the past and asserted "we must work with our partners around the world to stand up for our values and for our freedom".

At least 84 people, including several children, have been killed and dozens more hurt after a man drove a lorry into crowds gathered to celebrate Bastille Day along the famous Promenade Des Anglais in the French seaside city.

London Security Reviewed After Nice

Fifty more youngsters are being treated at the children's hospital in Nice, some with "life and death" injuries, following Thursday night's massacre.

:: Live: Witnesses Heard Children Screaming

Mrs May said she was "shocked and saddened by the horrifying attack".

"Our hearts go out to the French people and all those who have lost loved ones or been injured," she said.

"These were innocent victims enjoying a national celebration with their friends and families."

Dozens Dead In Nice As Truck Hits Crowd

She continued: "We are working urgently to establish whether any British nationals were caught up in the attack.

"Our ambassador is travelling to Nice today with consular staff and they will be doing all they can to help anyone affected."

Moments later her spokesman confirmed a small number of Britons had been "affected" in the attack.

He added the Government's emergency committee had convened on Friday morning to discuss any implications of the atrocity, on British soil.

The National Police Chiefs' Council revealed forces were reviewing the policing of large public events over the next seven days "to ensure the appropriate security is in place".

Speaking on a visit to Gatwick Airport, London Mayor Sadiq Khan also moved to reassure all Londoners.

He pledged he and the Metropolitan Police Commissioner would "do everything possible to keep Londoners safe".

Boris Johnson Reacts To Attack In Nice

"After Brussels, after Istanbul, after Nice, the police and security experts rightly review measures to make sure we are safe," he said.

"The police need to make sure that we learn any lessons possible from attacks elsewhere around the world.

"It is really important that we don't allow those involved in this evil and cowardly attack to change the way we live our lives.

"We are not going to allow the fact that we are a community where Christians, Jews, Muslims, Sikhs, Hindus, Buddhists, those not members of organised faith, get together, respect and embrace each other - we are not going to allow them to win."

Image: Bodies on a street after the deadly attack in Nice Image: The horrific scenes unfolded during Bastille Day celebrations Image: Picture from @Nice_Matin Twitter account showing the damaged truck in the aftermath Image: A major security operation is under way on the streets of Nice Image: French soldiers and police secure the area Image: Witnesses described chaotic scenes Image: People were filmed running from the area Image: More people running for their lives Image: Troops on a street in Nice Image: Image from @Nice_Matin showing emergency services personnel at the scene Image: Picture from Nice-Matin's Twitter account showing the aftermath Image: French President Francois Hollande leads an emergency meeting in Paris /

He added: "There are lots of Londoners of French origin. They are Londoners - they have friends and family in France.

"All of London will be thinking about the people of Nice today."

Meanwhile, Germany said it was beefing up its border controls at airports, as well as road and rail crossings into France, and Prime Minister Charles Michel said security was also being stepped up in Belgium ahead of a national holiday on 21 July.