Over 800 Islamists have left Germany for extremist strongholds in the Middle East, according to German national daily newspaper, Die Welt.

An astounding 60 percent of those were German citizens, approximately one-third of whom have already returned to Germany, the paper said.

The numbers have alarmed German and European authorities who are scrambling to prevent these statistics from growing further.

A majority of those who left for Iraq and Syria were males between 22 and 25 years of age and one-sixth were Muslim converts, a recent German Federal Criminal Police Office (BKA) study on 677 Islamists revealed.

As many as 130 of the Islamists have been killed in suicide bombing missions in extremist areas while German police continue to cope with the threats posed by the remaining and returning jihadis.

A congressional report issued last September noted that at least 250 Americans have left the U.S. and joined ISIS.

A further 80 have been arrested in the U.S. on charges of trying to join the Islamic State and/or attempting to provide material support.

The Obama administration and the U.S. Justice Department are coordinating a summit Wednesday with government officials and advertising executives to discuss measures aimed at countering the Islamic State’s recruitment drive.