LONDON -- Britain stepped up security at ports, following a shooting at the office of Paris-based satirical publication Charlie Hebdo on Wednesday in which 12 people were killed.
Downing Street said on Thursday that security was increased in the UK. However, there is no specific threat, and the terror alert will remain at "severe," which warns that an attack is highly likely. The level was last increased in August 2014.
A spokesperson said more cars and trucks would be searched, and that the security presence at Calais, a major ferry port in northern France, and the Eurostar terminal in Paris would be more visible.
The decision came after a COBRA meeting, chaired by UK Home Secretary Theresa May. Afterward, she said a terrorist attack in the UK was highly likely, and asked the public to remain vigilant.
UK Prime Minister David Cameron said on Wednesday that police and intelligence agencies would be looking at the situation to see if anything more can be done.
"We have to all be vigilant. We have to try to address all the problems of radicalisation that have happened in our country. We have to make sure we invest in our security and intelligence agencies properly. We have to deal with the problems at source," he said.
Cameron added that the events in Paris were different from some of the plots seen in the UK from "so-called home-grown terrorists."
Meanwhile, there were further signs of solidarity in the UK with those killed in the Paris attack.
Number 10 is flying the Union flags at half mast today. We stand united with the French people following the horrific killings in Paris.— David Cameron (@David_Cameron) January 8, 2015
Police officers around Britain observed a two-minute silence at 10:30 a.m. GMT.
Met Officers observe 2 minute silence #PoliceTributeToParis outside New Scotland Yard #CharlieHebdo pic.twitter.com/MyqfcWnPvb— Metropolitan Police (@metpoliceuk) January 8, 2015
On Wednesday night, hundreds of people turned out in London's Trafalgar Square for an impromptu vigil, following the attack.