Such documents represent an additional security risk for European states grappling with a large influx of refugees from countries including Syria and Iraq because they are harder to identify than outright fakes.
One diplomat said the list contained serial numbers of thousands of genuine blank passports that were held in government offices in parts of Syria and Iraq which have since been captured by armed groups including Islamic State.
The diplomat said there were around 5,000 missing Syrian passports from Raqqa and Deir al-Zor provinces on the list and 10,000 Iraqi ones from areas of Anbar, Nineveh and Tikrit.