(FILES) This file photo taken on November 16, 2015 shows an alternative crop of an undated picture from the February 2015 issue 7 of the Islamic State (IS) group online English-language magazine Dabiq, purportedly showing 27-year-old Belgian IS group leading militant Abdelhamid Abaaoud, also known as Abu Umar al-Baljiki and believed to be the mastermind of a jihadist cell dismantled in Belgium in January 2015, posing at an undisclosed location to illustrate an interview he gave to the magazine. An Islamic State leader with "direct" ties to the alleged mastermind of the Paris attacks was among 10 of the group's higher-ups killed in Syria and Iraq this month, the Pentagon said on December 29, 2015. / AFP / DABIQ / -

The number of Islamist militant fighters returning to Germany from Syria and Iraq is on the rise and more than 400 people are being watched, the head of German police said on Friday.

Holger Muench, president of the BKA federal police, told ARD television that the number of people leaving Germany for the two countries to fight with militant groups such as Islamic State was dropping.

But there has been a simultaneous rise in the number of fighters returning home.

“The wave of departures is becoming flatter,” he said. “In the meantime, we have more than 400 individuals who pose a threat and whom we must keep an eye on.” Muench said, however, that the suicide bombing in Istanbul this week in which 10 German tourists were killed was not a sign that the threat of a militant attack in Germany was higher than before.

The attack was carried out by an Islamic State suicide bomber who entered Turkey as a refugee from Syria, the Turkish government said, adding that the militant had not specifically target Germans.

Germany and Turkey are both part of a U.S.-led military coalition that is carrying out air strikes against Islamic State.