This photo provided by The Paris Police Prefecture Thursday, Jan.8, 2015 shows the suspects Cherif, left, and Said Kouachi in the newspaper attack along with a plea for witnesses (Photo: AP)
The two main suspects in the attack on France's Charlie Hebdo satirical magazine were reportedly on the UK terrorist list.
The BBC quoted a security source as saying that brothers Cherif and Said Kouachi were on the UK Home Office “Warnings Index” for some time.
Anyone on the terror watchlist is barred from entering the UK, the source added.
The Kouachi brothers were killed after an armed stand-off with police at a warehouse in Dammartin-en-Goele, north of Paris.
The UK Home Office announced that British officials are in close contact with their French counterparts.
Prime Minister David Cameron has offered France “every assistance necessary, including the full cooperation of our police and security and intelligence agencies.”
Theresa May, the UK home secretary, will attend a meeting of interior ministers of Europe and the US in Paris Sunday “to discuss the international response to the Charlie Hebdo attack.”
After the terror attacks in France, security has been tightened on the French-British sides of the English Channel in what May described as a precautionary measure.
The terror alert level in the UK remains at "severe", meaning a terrorist attack is "highly likely."
Meanwhile, the UK government announced it will allocate more financial resources to the security services to protect the country from terrorist activities.
Chancellor of the Exchequeur George Osborne has described tackling terrorism as “the national priority." He confirmed an extra £100 million had already been allocated to monitoring Britons going to Syria and Iraq.
The step came after Andrew Parker, the head of Mi5, the internal security service, warned that Al-Qaeda is plotting to massacre huge numbers of civilians in the UK and other Western countries.
Parker said it is too early to ascertain the precise details or origins of any attack, but it is a terrible reminder of the intentions of those who wish to harm the UK and other Western states.
“While the so-called Islamic State is the newest threat to the West and that self-started lone wolf plots are hard to foil, Al-Qaeda still has ambitions for something more spectacular,” Parker said in a briefing, attended by security experts.
He said his ”sharpest concern" as director general of Mi5 is "the growing gap between the increasingly challenging threat [of terrorism] and the decreasing availability of capabilities to address it.”