Cameron held a meeting on Monday morning to review the Paris attacks to assess the risks of something similar happening in Britain at which the police and other agencies agreed to update their training exercises for such incidents.
"They also discussed the risk posed by firearms, agreeing ... that we should step up our efforts with other countries to crack down on the illegal smuggling of weapons across borders," a spokesman for Cameron said.
The Paris attacks, in which journalists and policemen were among those killed, began with a shooting attack on the satirical newspaper Charlie Hebdo on Wednesday, January 7, and ended with a hostage-taking at a kosher supermarket on Friday.
Britain raised its terrorism alert in August to the second-highest level, meaning an attack is "highly likely".
The head of Britain's MI5 Security Service said last week that Al-Qaeda militants in Syria were plotting attacks to inflict mass casualties in the West.