Injured people are assisted after an incident on Westminster Bridge in London
Injured people are assisted after an incident on Westminster Bridge, on March 22, 2017.Toby Melville—Reuters
Injured people are assisted after an incident on Westminster Bridge in London
A woman lies injured after a shotting incident on Westminster Bridge in London
APTOPIX Britain Parliament Incident
Palace of Westminster incident
A woman assist an injured person after an incident on Westminster Bridge in London
Firearms Incident Takes Place Outside Parliament
Palace of Westminster incident
Injured people are assisted after an incident on Westminster Bridge, on March 22, 2017.
Toby Melville—Reuters
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See the Aftermath of the London Attack Near the United Kingdom's Parliament

Britain's parliament was on lockdown Wednesday after an attacker stabbed a police officer and was subsequently shot by police.

Around the same time on Westminster Bridge, near parliament, a vehicle struck several people, leaving one woman dead and several others with "catastrophic" injuries, officials said.

Until proven otherwise, London police are treating the incident as a terrorist attack, London Mayor Sadiq Khan said in a statement.

"The Metropolitan Police Service is dealing with the incident and urgent investigation is underway. My thoughts are with those affected and their families," Khan said in his statement, which he posted on Twitter.

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