"Passenger aircraft remain a primary target for some terrorist groups," said the UK government in its new five-year Strategic Defence and Security Review, published on Monday.
"Some groups, especially ISIL and Al Qa’ida, will also try to acquire chemical, biological and radiological capabilities."
Presenting the 'National Security Strategy' to the British parliament on Monday, Prime Minister David Cameron pledged to increase defense spending to meet the NATO target of two percent of GDP, and spend £178 billion ($270 billion) over the next decade on equipment and equipment support.
The British government estimates that approximately 800 British nationals have traveled to Syria to take part in the conflict there since it began, and many have joined ISIL or other terrorist groups.
"A large proportion were previously unknown to the police and security agencies. Of those who are known to have traveled about half have returned. Some of these, and many of those who remain in Syria, pose a threat to our security," the government stated on Monday.
