The British government said today that it has increased border security in response to the attack on the Charlie Hebdo newspaper in Paris yesterday.

A spokesperson for David Cameron said the measures included increased security at British checkpoints at the French port of Calais and at the Eurostar terminal in Paris, adding that Britain had sent a police counter-terrorism expert to France.

Home Secretary Theresa May said the decision had not been made in response to specific intelligence. Britain's threat alert was already at its second highest level (severe) before the attack, which means that an attack is highly likely. It has not been changed despite Cameron warning yesterday that it might be.

"Following the attacks we took the precautionary step yesterday of increasing security at the French-UK border," May said. "Officers from border force, the police and other organisations operating at the UK border have intensified checks on passengers, on vehicles, and on goods coming from France and other parts of Europe."

Britain's emergency response committee Cobra met to discuss the Paris attack in which 12 people were killed. May chaired the meeting, which heard briefings from intelligence agencies and national security advisers.

Cameron has said militants returning from Syria and Iraq pose the biggest risk to the country's security. He said at a press conference yesterday: "There is no one single answer to these appalling terrorist attacks. We have to all be vigilant. We have to try to address all the problems of radicalisation that have happened in our country."

The prime minister's spokesperson said police experts were ready to talk to British media outlets who had concerns about their security.

Additional reporting by Reuters