We will never let these cowards win: London Mayor

"We are all shocked and angry today - but this is our city. We will never let these cowards win and we will never be cowed by terrorism," the Mayor tweeted.

  Police have arrested 12 people in connection with the terror attacks incident which rocked London city on Saturday.

"The arrests in Barking, east London, followed a raid by police at a flat owned by one of the three attackers," BBC reported.

In a series of deadly attacks by Islamist terrorists, at least seven people were killed and 48 wounded in London on Saturday night, prompting British Prime Minister Theresa May to urge citizens to unite and fight in defeating the Islamist ideology of perversion of truth.

"As a country, our response must be as it has always been when we have been confronted by violence. We must come together, we must pull together, and united we will take on and defeat our enemies," the British Prime Minister said in a statement.

May said enough is enough and defeating the threat from the Islamist extremism is the biggest challenge.

"First, while the recent attacks are not connected by common networks, they are connected in one important sense. They are bound together by the single evil ideology of Islamist extremism that preaches hatred, sows division and promotes sectarianism," she said in a statement following the attacks in which three masked terrorists ploughed a van into pedestrians on London Bridge and then jumped out and went on a stabbing spree in nearby bars and restaurants.

"It is an ideology that claims our Western values of freedom, democracy and human rights are incompatible with the religion of Islam. It is an ideology that is a perversion of Islam and a perversion of the truth," she said.

In the latest attacks, suspected attackers wore fake explosive vests to scare away police and ran the vehicle into pedestrians. All three suspects were shot dead by police, said officials.

The incidents occurred at London Bridge and Borough Market when in one of the attacks the white van ploughed into pedestrians on London Bridge at about 10.08 pm, said reports.

The suspects reportedly also stabbed people and a police officer after jumping out of the van.