European intelligence services believe that there are up to 20 jihadist sleeper cells planning to carry out attacks in France, Germany, Belgium and the Netherlands, according to a senior Western official.
The official, speaking on condition of anonymity, was quoted by CNN as saying that there are approximately 120-180 jihadists involved in the cells across Western Europe who are awaiting orders to attack.
The threat of a terror attack on Belgium was classed as "imminent", the official said, adding that the Netherlands was also at great risk of an attack.
The jihadists who were neutralised in Verviers were allegedly planning to kill policemen in the street and at police stations, according to Belgian prosecutors.
Two jihadists were killed in the raid and 13 suspects have been arrested in the aftermath.
Federal prosecutor Eric Van der Sypt said that there was "no link at this stage to the Paris attacks" which saw three gunmen kill 17 people last week.
Although no direct link has been proven between the two cells, the Kouachi brothers - who attacked the offices of Charlie Hebdo - purchased their weapons from an underground arms dealer in Belgium, it has been revealed.
A senior Belgian counterterrorism official told CNN that the terror cell in Verviers was most likely linked to Islamic State.
They were allegedly given instructions by IS members to conduct attacks in Europe in response to the US-led coalition's air strikes against the group's positions in Syria and Iraq.