Tiyach and Tayach is a company that specializes in preservation and restoration projects of historical buildings in Israel.
One of its projects is to restore the historic Hassan Bek mosque in Jaffa.
Its description of the history of the mosque includes a disturbing detail: (apparently taken verbatim and autotranslated from the Wikipedia Hebrew page on the mosque):
Between 1914 and 1916 Hassan Bek built a magnificent mosque in the northern part of Jaffa, in the Manshiyeh neighborhood, to block the expansion of Tel Aviv.
The mosque, designed by Ben Zion Gini, the Jewish city engineer in Jaffa, was built with a tower disproportionately high for the building itself, and it controls all of its surroundings.
For the purpose of establishing the mosque, which he dedicated to himself, Hassan Beck employed a lot of forced laborers (a custom in the Ottoman Empire), which he ordered to work day and night to complete the task quickly.
The effort was so great that many of them were injured or even died during the construction.
...
Construction materials were taken from residents of the area who were forced to sign that they give the materials as a gift.
During the mosque construction, Ottoman army soldiers kidnapped Jewish youths from Tel Aviv and especially from the “Yemenite vineyards” for forced construction of the mosque.
Two of these young men were: Zechariah (Yahya) Valani and Shalom (Salem) Massuari.
Hassan Bek did not finish the construction of the mosque before he left his post in March 1916.
The Supreme Muslim Council, which understood the importance of the mosque for the Arab national cause, invested the necessary funds and the construction of the mosque ended in 1923.
Officially, the Ottoman empire ended slavery in the late 19th century but I cannot find any other source at this time of forced laborers for Islamic or state projects.
If accurate, this is a disturbing chapter in history that has not been researched fully.
(h/t Michelle)