Islamic State extremists have issued a call to war against Turkey, urging supporters in the country to rise up and conquer Istanbul, the country's largest city.
In a seven-minute video titled "A Message to Turkey," the group slams the country's president, Recep Tayyib Erdogan, as a traitor "working day and night to hand over" the city it refers to as Constantinople to the "Crusaders."
The video, which was released Monday by Islamic State's media office in the Syrian city of Raqqah, has raised alarm in neighboring Turkey, where many suspect the existence of sleeper cells in southern cities such as Gaziantep and Kilis.
Police found a drone, night vision scopes, ammunition clips and camouflage clothing in raids Tuesday on suspected Islamic State cells in Gaziantep province, the Turkish news outlet Today's Zaman reported. Four people were detained, the report said.
Last month, Ankara announced that it was stepping up action against Islamic State, including launching airstrikes against fighters in Syria and allowing a U.S.-led coalition to use an air base for bombing runs against the militants.
A gray-bearded militant speaking in fluent Turkish opens the new video. Peppering his remarks with verses from the Koran, he laments that Turkey, which he says was once strong because of its support of Islam, has turned to secularism.
He then accuses Erdogan of siding with "the American Crusaders, the caretakers of the Jews," as well as rival Syrian rebel groups, including the Western-supported Free Syrian Army and Islamist factions such as Jaish Al Islam, or the Army of Islam.
However, he appears to see the greatest threat as coming from the "criminal atheists" of the Kurdistan Workers Party, or PKK, an ethnic Kurdish militant group that has waged a decades-long insurgency against the Turkish government.
If Erdogan "continues on this path of betrayal to preserve his [power], soon you will see the east of the country in the hands of the atheist PKK and its west in the hands of the worshipers of the cross," warns the militant, as the U.S. and PKK flags slowly spread across a map of Turkey.
"O people of Turkey, you must rise and fight those Crusaders and atheists ... who tricked you and made you slaves of the Crusaders; you must fight them before it is too late," he says.
Turkey's decision to take a more forceful role against Islamic State was a significant shift for the country, which has long been accused of turning a blind eye to, if not actively supporting the militants operating along its 500-mile frontier with Syria.
Turkey, a U.S. ally and member of the North Atlantic Treaty Organization, has become the main crossing point for would-be militants coming from Europe and other regions to live under the group's self-proclaimed caliph, Abu Bakr Baghdadi.
In July, however, Islamic State was blamed for a suicide bombing in the Turkish border town of Suruc that killed at least 33 people.
Turkish warplanes retaliated with bombing runs on Islamic State positions in Syria, while Turkish police rounded up hundreds of people with suspected links to the extremist group.
Earlier this month, six U.S. F-16 fighter jets landed at Turkey's Incirlik Air Base with about 300 personnel to join the U.S.-led coalition fighting Islamic State, according to the Pentagon. Last week, they flew their first sorties in Syria -- a fact that the Turkish-speaking militant in the video notes with anger.
"The traitor Erdogan has ... opened up the military bases of Turkey to the Crusaders and their planes to bomb the people of Islam in Syria and protect the atheist PKK," rails the militant, who is flanked by two companions.
Despite these steps, however, Kurds have continued to accuse Ankara of colluding with Islamic State to thwart the establishment of an independent Kurdish state across the border in Syria -- charges denied by Turkey.
Since last month, Turkish authorities have focused much of their firepower on the PKK, ending a fragile two-year cease-fire with a devastating air campaign against the group's positions in northern Iraq. PKK fighters have responded with a wave of attacks against Turkish officials.
Bulos is a special correspondent. Staff writer Alexandra Zavis in Los Angeles contributed to this report.