Nine are held in custody following the London attack. Police confirm the assailant was born Adrian Russell Elms.
British police have made two further arrests and released one woman on bail taking the total number being held in custody over the London attack to nine.
Five people died in the ISIL-claimed assault in Westminster including the UK-born assailant, Khalid Masood.
The Metropolitan police’s counter terrorism chief, Mark Rowley, confirmed Masood went by a number of aliases, but was born Adrian Russell Elms, before taking his stepfather’s surname, Ajao.
Questions remain about his motives:
“Our investigation focusses on understanding his motivation, his preparation and his associates. Clearly a main line of our investigation is what led him to be radicalised? Was it through influences in our community, influences overseas or through online propaganda? Our investigations and arrests will help with that,” said Rowley.
He named the fourth victim as 75-year-old Leslie Rhodes, from south London.
At least 50 people of some 12 nationalities were injured as the attacker drove a car into pedestrians on Westminster Bridge, before continuing on foot and fatally stabbing police officer Keith Palmer.
Two remain in hospital in a critical condition and one is considered to have life-threatening injuries.