Ankara, Turkey ? Attack helicopters buzzed over a region in southeastern Turkey on Sunday looking for Kurdish rebels after troops reportedly killed 15 separatist guerrillas in a morning operation far from the increasingly tense border with Iraq.

The fighting occurred in the predominantly Kurdish province of Tunceli, as the government pressed on with its efforts against the Kurdistan Worker’s Party, or PKK, whose fighters have killed at least 42 people in the past month in raids on Turkish territory.

Turkey has threatened to send troops into Iraq to hunt down the rebels, and has demanded the extradition of PKK leaders. The United States, Iraq and other countries have been pressing for Turkey to refrain from cross-border operations.

The top American commander in Iraq, Gen. David Petraeus, said Sunday the U.S. military was playing a role in trying to defuse the tensions, but he declined to elaborate. “I am actually not going to say anything about what we may be doing with our long-standing NATO allies Turkey, although we clearly are doing things with them,” he said.

The comments seemed aimed at allaying Turkish frustration, piqued on Friday when the American military commander in northern Iraq, Maj. Gen. Benjamin Mixon, said he planned to do “absolutely nothing” to counter Kurdish rebels operating from the region.

Mixon handed over regional command to Maj. Gen. Mark Hertling on Sunday as scheduled. After the ceremony, Hertling told reporters that it would be “inappropriate” for him to discuss possible military measures while “diplomatic efforts are ongoing.”

In Turkey, pressure has been building on Prime Minister Recep Tayyip Erdogan to take action, with tens of thousands of Turks staging anti-PKK protests in recent weeks.

Erdogan called for unity between Turks and his country’s minority Kurds Sunday, but reiterated his government’s determination to fight Iraq-based separatist Kurdish rebels.

“As long as we are firmly bound together, the treacherous separatist terrorist attacks will never reach their goal,” Erdogan said in a message ahead of today’s celebrations to mark the 84th anniversary of the Turkish republic.