LONDON • Europol, the European police agency based in The Hague, Netherlands, will create a new unit next month to discover and dismantle social media accounts used by Islamist radicals to spread their message and recruit foreigners.

The unit will have about 15 officers from Europol and national police forces at first, and will be gradually enlarged over the next year, the agency announced on Wednesday. The task is to scour the Internet for accounts set up by radicals, including those from the Islamic State in Iraq and Syria (ISIS).

The number of Facebook, Twitter and other social media accounts connected to ISIS is estimated to be in the tens of thousands, with the Twitter accounts sending out as many as 100,000 posts a day.

Europol director Rob Wainwright said the agency will cooperate with member states, national intelligence and police agencies, and social media and other private companies. He estimates that up to 5,000 people from Western Europe have travelled to Syria and Iraq, many to join ISIS.

British officials believe that up to half of the 500 or so Britons who have done so have already returned home and represent potential threats.

NEW YORK TIMES