FILE PHOTO: European Commissioner for Migration and Home Affairs Dimitris Avramopoulos addresses a news conference on the European Agenda on Migration at the European Commission headquarters in Brussels, September 6, 2017. REUTERS/Francois Lenoir

BRUSSELS (Reuters) - The European Union’s executive offered initial backing on Thursday to a Franco-German proposal to allow more permanent border checks within the bloc’s free-travel zone.

Five countries in the so-called Schengen travel zone - Germany, France, Denmark, Austria and Norway - restarted border controls after 2015 attacks in Paris and in an attempt to control the movement of refugees and migrants arriving in the bloc in unprecedented numbers the same year.

Schengen rules allow for the reintroduction of such frontier controls for up to two years and the ones now in place expire in November.

Germany and France, aiming for an extension and the ability to reinstate them in future, asked the EU to change the system to extend the maximum duration to four years.

A joint proposal by Paris and Berlin, seen by Reuters, says that would be required “in the context of a long-term terrorist threat” after a raft of deadly Islamist attacks in Europe.

“The Commission recognizes that new security challenges have appeared in the past years, as demonstrated by the recent terrorist attacks in Barcelona and Turku,” the EU’s migration chief, Dimitris Avramopoulos, told journalists after talks with EU’s interior ministers.

He said the Brussels-based Commission would propose an update to the Schengen borders code later this month.

French Interior Minister Gerard Collomb told journalists after the talks in Brussels:

“We had raised this problem some time ago with my German colleague ... and from what I heard from the Commissioner he indeed wants to make the Schengen code more flexible ... to allow us to protect our borders against terrorism.”