This was announced by a reporter of American news network CNN.
"There's intelligence that has been obtained by European security agencies that ISIS in Syria and Iraq is aiming to hit the United Kingdom next," said Paul Cruickshank, a terrorism analyst of CNN.
"The intelligence suggesting that British ISIS operatives in Syria and Iraq have been tasked to return to the United Kingdom to launch an attack against the UK.
The threat has come a day after Britain's House of Commons on Wednesday voted to support a government motion on extending Britain airstrikes against the Islamic State (IS) to Syria after 10 hours of intense debate.
The decision to extend air strikes against ISIS is being treated very seriously by the group.
Meanwhile, a radicalisation expert has warned the UK is under threat from home-grown jihadis who could carry out similar attacks as the Paris atrocities.
Following the attacks in Paris on November 13 the threat of terrorism is spreading from the war-torn Middle East to mainland Europe. At least 130 people were killed in the Paris attacks.