BEIRUT (AP) -- Kurdish-led Syrian forces backed by the U.S. said they have begun a military campaign to liberate the Islamic State group's de facto capital of Raqqa, urging civilians to avoid "enemy gatherings" in the Syrian city and warning Turkey not to interfere in the operation.
The announcement by a coalition of Kurds and Arabs known as the Syria Democratic Forces came at a news conference in Ein Issa, north of Raqqa, and was attended by senior commanders and representatives of the group. But it lacked specific details on how they plan to oust the militants from the city, which is home to nearly 200,000 mostly Sunni Arabs and an estimated 5,000 militants.
Islamic State forces already are under attack by U.S.-backed Iraqi forces on the eastern edges of the city of Mosul, which the militant group seized in 2014 when it captured territory across Iraq and Syria for its self-proclaimed caliphate. The Iraqi forces, who began their operation Oct. 17, are trying to push deeper into the city, which is the militants' last urban bastion in Iraq.
Kurdish officials said the two anti-IS campaigns are not coordinated but simply a matter of "good timing."
"We call on our heroic steadfast people in Raqqa and surrounding areas to stay away from enemy gatherings which will be a target for the liberating forces and the coalition forces, and to head to areas that will be liberated," said Cihan Ehmed, an SDF fighter reading the statement.
She said 30,000 fighters will take part in the operation, dubbed "Euphrates Rage," and that a joint operations command had been set up to coordinate various factions on all fronts.
The SDF is dominated by the main Syrian Kurdish fighting force known as the People's Protection Units, or YPG. The United States considers the group to be the most effective force against the IS, but Turkey views it as a terrorist organization and claims it's linked to Turkey's outlawed Kurdish group. Turkish officials including President Recep Tayip Erdogan have said they will not accept a role for the Kurds in the liberation of Raqqa.
Turkey's defense minister last week suggested that instead of the Kurds, Turkish-backed forces can present an "alternative."
But Kurdish officials have rejected any role in the Raqqa campaign for Turkey or the opposition forces it backs inside Syria, and U.S. officials have also acknowledged that the YPG will be a major part of any Raqqa offensive.
"Our hope is that the Turkish state will not interfere in the internal affairs of Syria," Ahmad said at the news conference, suggesting SDF forces would defend themselves if it did. "Raqqa will be free by its own sons."
There was no immediate comment from Turkey, the U.S. or the Syrian government of President Bashar Assad on the Kurdish announcement.
SDF spokesman Talal Sillo told The Associated Press that the Raqqa campaign will occur on several fronts.
"We want to liberate the surrounding countryside, then encircle the city, then we will assault and liberate it," he said. Asked whether he had assurances from the U.S. that Turkey or other forces will not interfere, he replied: "Of course, to begin the operation, we have made sure there will be no other forces but the SDF in the operation."
Another SDF official, Rezan Hiddo, said Turkey has been an "obstacle" to the Raqqa campaign all along. He said the SDF has informed the international coalition that Turkey could spoil the campaign if it decides to strike at Kurdish-controlled areas in northern Syria. This would force the Kurds to stop their campaign toward Raqqa to protect their areas, he said.
"We cannot extinguish the fire in our neighbor's house if our home is burning," he added.
U.S. officials have acknowledged that ousting IS from Raqqa poses tougher political challenges than the Mosul offensive, and have suggested the initial stage would involve isolating the city before any forces try to move in.
The commander of anti-IS coalition forces, Lt. Gen. Stephen Townsend, said last week that U.S. intelligence has detected signs that Islamic State attacks against Western targets are being plotted from Raqqa, adding urgency to coalition plans to encircle and eventually assault the city.
"We know this plot-and-planning is emanating from Raqqa. We think we've got to get to Raqqa pretty soon."
But coalition leaders have been struggling with the timing for the Raqqa campaign, not only because of the demands of the large Iraqi-led Mosul operation but also because the political and military landscape in Syria is more complicated amid a civil war that has lasted more than five years and has devastated much of the country.
Townsend said more Syrian opposition fighters need to be recruited, trained and equipped for the Raqqa battle, but he and other officials have said in recent days that the Mosul and Raqqa operations will overlap.
Unlike in Iraq, where the coalition has a coherent government to work with, the U.S. and its coalition partners in Syria are relying on a hodgepodge of local Arab and Kurdish opposition groups, some of which are fierce rivals. The tensions are exacerbated by the presence of Russian and Syrian forces on one side and Turkish forces on another.
Townsend said, however, that the YPG will necessarily be part of the offensive.
"The facts are these: The only force that is capable on any near-term timeline is the Syrian Democratic Forces, of which the YPG are a significant portion," he said.