British police said Friday they had arrested two more suspects related to the London attack, the deadliest in Britain since the 2005 London suicide bombings that killed 52 people.
A top anti-terror officer says two more "significant arrests" have been made in connection with the London attack.
Nine people remain in custody and one woman has been released on bail, Rowley said.
Police said Masood was born in the county of Kent in southeast England and was most recently living in the West Midlands region of central England.
Russian investigators confirm identity of metro bomber
Russia's top investigative body said in a statement it had identified the suspected bomber but did not disclose his details. In the past 20 years, Russian trains and planes have been frequent targets of attack, usually blamed on Islamic militants.
Authorities on Thursday identified a 52-year-old Briton as the man who mowed down pedestrians and stabbed a policeman to death outside Parliament in London, saying he had a long criminal record and once was investigated for extremism - but was not now on a terrorism watch list. After stabbing a police officer, who was later confirmed dead at the scene, the attacker was shot.
"We still believe that Masood acted alone on the day and there is no information or intelligence to suggest there are further attacks planned", said Met police Indian-origin Deputy Assistant Commissioner Neil Basu, who is the Senior National Coordinator for UK Counter Terrorism Policing.
On Thursday, the self-described Islamic State issued a claim of responsibility for the attack through its Amaq news agency.
His first conviction was in November 1983 for criminal damage and his last conviction was in December 2003 for possession of a knife, Metropolitan Police said.
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BMW wasn't among the top 50 advertisers on "The O'Reilly Factor", but Mercedes-Benz and Hyundai were regular spenders. O'Reilly, perhaps notably though not surprisingly, did not address the Times report on his Monday evening show.
Some media said Masood, reportedly a married father-of-three, was believed to have worked as an English teacher and had given that as his occupation when he rented the vehicle used in Wednesday's bloody rampage.
Police continue to search five addresses and another 16 searches have concluded, in what Rowley said was a fast-moving and wide-ranging investigation.
On Wednesday night seven people were arrested on suspicion of the preparation of terrorist acts - including three women and four men ages between 21 and 39-years-old. Trucks driven into crowds in France and Germany killed a total of almost 100 people in 2016, and ISIS has repeatedly urged its supporters to use ramming attacks as a means of killing civilians.
A massive police investigation is under way after a terror attack in central London. Also on Friday, a 75-year-old pensioner became the fifth person to die in the Westminster attack.
Scores reported dead in Syria gas attack
The attack killed at least 58 Syrians , including women and children, according to the Syrian Observatory for Human Rights . The Syrian army categorically denied launching such a toxic attack, the Syrian state news agency SANA reported on Tuesday.