Today is the first anniversary of the Brussels attack.
One woman confirmed dead so far. Others are in a "devastating" condition.
Another woman pulled alive from Thames and treated by paramedics.
Conservative MP Tobias Ellwood battled to save the life of police officer.
Met Commander BJ Harrington is making a statement. He says although he is "open-minded" to the motives, it is being treated as a terrorist incident.
Prime Minister Theresa May, who was bundled into her car and driven away as the attacks started, will chair a meeting of the Government's emergency Cobra committee later today, a Downing Street spokesman said.
Latest pictures show people being supervised by police as they are allowed to leave the Palace of Westminster:
The Daily Mirror says this is the suspect: