LATEST: London terror attack - what we know so far
Here is what we know so far about the terror attack in London today.
Parliament is in lockdown after an attacker stabbed a police officer before being shot by armed police in Westminster.
The knife attack and shooting came shortly after about a dozen people were mowed down by a car on Westminster Bridge.
The car reportedly later drove into the railings at Parliament Square. Scotland Year said they are treating it as a terrorist incident until they "know otherwise."
Gunshots were heard outside the Palace of Westminster after a knifeman man reportedly ran through the gates into the front yard of the parliamentary compound.
Two people were seen being treated on the ground in New Palace Yard amid shouts and screams.
Prime Minister Theresa May was bundled into a car by plain-clothed police officers and taken to safety. It is known that Mrs May is safe.
The House of Commons has been suspended for the day, while MPs, including several from South Yorkshire, are being held inside the building.
An air ambulance later landed in Parliament Square as paramedics rushed to help multiple casualties.
Footage of Westminister Bridge shows at least four injured people lying on the pavement where police condors have been set up.
More to follow.