"We're doing all we can to keep Londoners safe," Mayor Sadiq Khan
told CNN's Christiane Amanpour
. "We're doing all that we can to keep visitors safe. We're doing all that we can to keep our city safe."
In promising a visibly heightened police presence, the mayor praised the officer killed in Wednesday's attack
, which left two others dead and at least 40 injured.
"One of the reasons I can say London is the safest global city in the world and one of the safest cities in the world is because there are literally tens of thousands of Keith Palmers keeping our cities safe, working with members of the public who provide intelligence and information, working with our security services," he said.
"One of the reasons why fewer people were killed, fewer people were injured is because of the bravery of our police service, the bravery of our emergency services and because we've practiced and prepared for events such as this," Khan said.
London 'returning to normal'
Eight people have been arrested so far as police continue to investigate the deadliest terror attack in central London in 12 years. Police shot and killed the perpetrator, who Prime Minister Theresa May said was British-born and had been linked to violent extremism, after he plowed a car through crowds
, then tried to storm Parliament.
Defending his city, Khan echoed comments he made shortly after the attack that terror incidents can unfold in anywhere. Those remarks
have drawn some criticism, including from Donald Trump Jr
"Terrorists hate the fact that whether it's New York, whether it's London, whether it's Paris ... we have diverse communities living together peacefully, getting on with each other, respecting each other," he said.
London is a "thriving democracy," and business would go on as usual today, Khan said.
"Parliament is returning to normal today," he said. "City Hall is returning today, tourists are returning to London today, businesses are returning to normal today -- just the thing the terrorists hate."