Officials investigating the Paris attacks believe the terror network who orchestrated the massacre, had links to people in the UK. Several people based in the UK are suspected of having connections to Abdelhamid Abaaoud, the Islamic State operative and alleged mastermind of the November 13 attacks.

According to officials cited by The Wall Street Journal, at least one person connected to the Paris attacks is believed to have travelled to the U.K. before the shootings. The suspects, some of whom are believed to be of Moroccan heritage, are based in Birmingham, the U.K.'s second-largest city which has known ties to Islamist extremism. Several Islamist terrorist cells of North African origin have been connected with the city and the surrounding region.

On November 13, eight suicide bombers unleashed a wave of atrocities on the French capital on six major sites including a street cafe and the Bataclan theatre which was the scene of a blood bath. 130 people died and hundreds more were injured. Reports linking suspects in the UK to the Paris attacks will fuel fears of a similar attack occuring in Britain.

In the aftermath of the Paris massacre, British Prime Minister David Cameron warned that London was a prime target for a mass assault by IS. In recent days he lobbied vigorously for the U.K. to join U.S.-led airstrikes against Islamic State in Syria, stating that the terror group poses a direct threat to the U.K.

The Paris attacks "could just as well have been in London as in Paris," Mr. Cameron said as Britain extended its bombing campaign against the militant group to Syria from Iraq.

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A vigil at the Place de la Republique in memory of the victims of the Paris attacks Christopher Furlong/Getty Images

In the wake of the Paris massacre, the UK government revealed it had thwarted seven terror attacks on British soil in the past year. The U.K.'s terror alert is at the second-highest level, "severe," which means an attack is highly likely. Security has been stepped up in the capital, with a strong police presence at major sites and tighter border checks to monitor the movement of people and vehicles entering the UK.

The U.K.'s most senior counterterror officer Mark Rowley said the Paris attacks were evidence of a network intending to strike at the heart of Europe.

"You would be expecting us and the security services to be working flat out to look for any possible links and connections of that network to anything in the U.K.," Mr. Rowley said. "I can give you 100% assurance we are doing that but it would be wrong to discuss the detail of what we are or are not finding."

Metropolitan Police officers stationed in Paris are helping with the French investigation.

The reports come as Belgian police continue to search for Salah Abdeslam, who fled across the border after the Paris attacks and Mohamed Abrini, who is suspected of having driven him to Paris. Officials are also looking for two new suspects connected to the Paris attacks who were using fake Belgian identification documents with the names Samir Bouzid and Soufiane Kayal, the federal prosecutors' office said.