Concern has risen since a Frenchman believed to have returned recently from fighting with rebels in Syria was arrested in May over the killing of four people at the Jewish Museum in Brussels.

The 28 heads of state or government will also urge the European Parliament urgently to adopt a plan for countries to share airline passenger data.

Lawmakers have resisted endorsing the system for sharing data, known as the Passenger Name Record (PNR), on the grounds it would infringe people's privacy.

Under pressure to drop their opposition in the wake of the Paris attacks, members of the European Parliament pledged in a resolution on Wednesday to aim to finish work on the PNR law by the end of this year.

The leaders will call for police to step up information sharing and closer cooperation between EU members' security services and in the fight against arms trafficking.

They will also urge EU governments to quickly implement stronger rules to prevent money-laundering and terrorist financing and to effectively freeze assets used for financing terrorism.

They will call for "adequate measures to be taken, in accordance with national constitutions, to detect and remove internet content promoting terrorism or extremism."