In the note, Obama expressed concern that American embassies and other installations in Turkey could be the target of attack over the film. The note, which was forwarded to Erdogan’s staff by a White House official, came three days after a U.S. diplomatic compound was attacked in Benghazi, Libya, resulting in the death of Ambassador Christopher Stevens and three other Americans.

Although an investigation later found the Benghazi attack was premeditated, initial suspicion fell on protesters angered by a YouTube video called the Innocence of Muslims. The video, created by a controversial Los Angeles filmmaker, angered Muslims in the Middle East over its depiction of the sacred prophet Mohammed. The note released on Monday by Syrian hackers revealed Obama’s concerns over protests stoked by the film’s release.

“Our embassies across the Middle East are at risk, and we are deeply concerned that after Friday prayers our people and installations in the region could be vulnerable to attack,” Obama wrote to Erdogan. “We must not let extremists use this video as a pretext to attack America or our other allies and partners.

Obama wrote that the U.S. government had nothing to do with the video and that its message “entirely contradicts my personal views and the values that America stands for.” But he also said that the government could not force YouTube and other websites to remove the video, saying the government was “bound by our commitment to free expression.” The Turkish government had sought to have the film removed from the Internet, going so far as to block YouTube for several weeks in order to restrict its citizen’s access to the video.

Still, Obama hoped that Ergodan would use his influence to call upon Muslims to demonstrate in a peaceful manner. “I would ask that you speak out immediately and forcefully before people go to Friday prayers today,” Obama wrote. “I believe that you are one of the most-credible voices in the Islamic world today, and that if people hear from you calling for calm and condemning violence, it will have a real impact.”

The message was one of hundreds leaked by the Syrian Electronic Army on Monday. A group spokesperson told The Desk it had compromised several dozen e-mail accounts belonging to Turkish officials.

LINK: Read the full letter sent by President Obama to Turkish PM Erdogan