The Islamic State in Iraq and Syria (ISIS) attacked the Syrian border town of Kobani from Turkey on Saturday, according to Kurdish officials and activists.
According to local reports and officials, a suicide bomber drove to a border crossing between Kobani and Turkey and detonated an armored vehicle, the Associated Press reported.
ISIS "used to attack the town from three sides," Kurdish Democratic Union Party spokesman Nawaf Khalil told the AP. "Today, they are attacking from four sides."
Kobani has been in danger of falling to the terrorist group for several months, raising questions over whether the U.S.'s strategy against ISIS is working and prompting U.S.-led airstrikes in an effort to save the Kurdish town.
Mustafa Bali, a Kobani-based activist, told the AP that ISIS has taken positions in grain silos on the Turkish side of the border, and are launching attacks towards the border crossing. He also said U.S.-led airstrikes were launched Saturday morning.
"It is now clear that Turkey is openly cooperating with Daesh," Bali said, using the Arabic acronym for the Islamic State.
Turkey denied in a statement the fighters entered Kobani from its territory, which would be a first for ISIS.
"Claims that the vehicle reached the border gate by crossing through Turkish soil are a lie," the statement said. "The security forces who are on alert in the border region have ... taken all necessary measures."
It is widely believed that most foreign fighters flowing into Syria have crossed the porous border from Turkey into Syria. Turkish officials have insisted they are doing all they can to stem the flow.
And although Turkey has aiding rebel fighters against the Assad regime in Syria, it has been reluctant to aid Kurdish fighters in Kobani out of fear of stoking a Kurdish nationalist movement within its own borders.