Paris has called for the European Union to improve passport checking procedures to ensure no more false Syrian passports are allowed through, especially in Greece and Italy, after two of Paris attackers were found to be carrying such documents.The attacks "unfortunately showed that some terrorists are trying to get into our countries and commit criminal acts by mixing in with the flow of migrants and refugees," French Interior Minister Bernard Cazeneuve said in a letter to the European Commission.He called for the EU to improve the quality of the equipment used to check travel documents at external borders, particularly in Greece and Italy, to allow the documents to be matched against databases of stolen or lost passports compiled by Interpol."The checks of travel documents presented by refugees at the external borders of the EU are an extremely significant and worrying issue," Cazeneuve added.The minister said blank passports were in circulation that were stolen from administrative facilities in places overrun by the Islamic State jihadist group. Once an identity had been added, "these 'real-fake' passports are very hard to detect", he said."Other passports have also been taken from dead people, such as Syrian soldiers or civilian victims of bombings and then sold to people resembling them," Cazeneuve added.Security checks in the refugee reception centres "remain largely insufficient", Cazeneuve said.