People light candles at a vigil in Trafalgar Square the day after an attack, in London, Britain March 23, 2017. [Photo/Agencies]

UNITED NATIONS - Following an attack on the Houses of Parliament in London, British Foreign Secretary Boris Johnson said here Thursday that internet providers and "great social media companies" are responsible in radicalization of terrorists.

Speaking to reporters after sitting as this month's president of the UN Security Council, where a minute of silence was held for victims of the fatal Westminster attack, Johnson was asked by a reporter "What could be done ... to stop people being radicalized by what they see on line?"

"The responsibility for this must lie with the internet providers and with those who are responsible for the great social media companies," Johnson said. "They got to look at the stuff that is going up on their sites."

The providers and social media firms should closely watch over and exam material being posted "to take it down where they can. Everybody has responsibility in this," the foreign secretary said.

"I do believe that we need to go through a period of reflection on how we transmit images of these events around the world in real-time," he added.

Five people, including a police officer and the attacker, were killed and at least 40 others injured by a single assailant in the London attack. Johnson called it an act staged "in a cowardly and in a despicable" psyche.

"You may know that today there are victims in London from 11 nations, which goes to show that an attack on London is an attack on the world," he said.

"From my talks here in the United States with the US government (Wednesday) and with partners from around the world that the world is united to defeat the people who launched this attack and to defeat their bankrupt and odious ideology."

Johnson sat as president during a session of the Security Council on Somalia, which he visited last week. Britain is the rotating president of the 15-member panel for the month of March.