The number of people arrested in Europe on suspicion of jihadist terror activities nearly doubled over the last two years, Europe's policing agency said Thursday, adding that actual attacks have decreased.

Some 718 were arrested on offences relating to jihadist terror last year as opposed to 395 in 2014, while jihadist attacks dropped from 17 in 2014 to 13 last year -- of which six were linked to the Islamic State group, Europol said in a new report.