Europe and the United States on Tuesday urged Turkey to show a "proportionate response" in the face of daily attacks by Kurdish militants amid growing concern over the scale of Ankara's air campaign against the rebels.
Two more Turkish soldiers were killed in the latest assault blamed on Kurdistan Workers Party (PKK) militants, as Ankara pressed on with a relentless air campaign against hideouts in northern Iraq.
Ankara is waging a two-pronged cross-border "anti-terror" bombing campaign against Islamic State (ISIS) terrorists in Syria and PKK rebels in northern Iraq.
But so far the raids have overwhelmingly targeted the Kurdish rebels, in what critics say is a pretext for Turkey to crack down on the Kurds – a move that comes after Ankara was shown to be cooperating with ISIS.
Official media in Turkey have said at least 260 PKK members have been killed so far, in hundreds of sorties targeted against the group's shelters, weapons stores and caves.
But concern over possible civilian casualties grew when pro-Kurdish media at the weekend said Turkey killed eight civilians by bombing a village. The army denied the claims.
The European Union's enlargement commissioner, Johannes Hahn, expressed "deep concern" at the impact on efforts to resolve the decades-long conflict with Turkey's Kurdish minority.
Turkey has a right "to react to any form of terrorism," Hahn said in a statement. Both the US and the EU list the PKK as a terror group.
But he added: "The response, however, must be proportionate, targeted and by no means endanger the democratic political dialogue."
He called on Turkey to refrain from any action "that could further destabilize the region."
In Washington, State Department spokesman Mark Toner told reporters Ankara had a right to self-defense against PKK attacks.
"We want to see the PKK renounce violence and re-engage in talks with the government of Turkey. And…we want to see the Turkish government respond proportionately," he said. Turkey has already indicated peace negotiations are over.
"Two more killed by PKK"
The current crisis began two weeks ago on July 20 when 32 young pro-Kurdish activists were killed in a Turkish town on the Syrian border in a suicide bombing blamed on ISIS.
The PKK, noting the government's collaboration with ISIS that was recently revealed by Western officials, shot dead two Turkish police in reprisal, and from there the wave of violence has escalated, shattering a 2013 ceasefire.
President Recep Tayyip Erdogan, who opponents accuse of orchestrating the crisis to boost his popularity after a recent election loss to pro-Kurd opponents, has said Turkey will do "whatever necessary" to defeat the militants.
In the latest violence blamed on the PKK, two soldiers were killed and two wounded on in southeast Turkey when a mine exploded under their convoy in Sirnak province.
According to an AFP toll, 19 members of the Turkish security forces have been killed in attacks blamed on the PKK since the current crisis began.
An explosion hit a natural gas pipeline transporting gas from Azerbaijan to Turkey in the eastern province of Kars, the Anatolia news agency said.
"Armed drones use Incirlik"
Meanwhile, Turkey's Western allies are also waiting for it to commence full-scale operations against ISIS targets in northern Syria, where just a handful of Turkish strikes have been officially reported.
A key pillar of the new cooperation with the United States is giving Washington the right to use Turkey's Incirlik air base for air strikes against ISIS targets.
In a major development, the Pentagon announced overnight that US armed drones had now taken off from Incirlik to conduct missions over northern Syria.
Dozens of piloted US jets are expected to arrive in the next days to ramp up the bombing raids, Turkish media have reported.
The US deputy special envoy for operations against ISIS, Brett McGurk, tweeted that the US had begun flying "armed ISR (Intelligence, Surveillance and Reconnaissance) missions" to strike ISIS terrorists in Syria.
"Just a start…" he added.
The violence also comes with Turkey still without a permanent government since June 7 legislative elections, when the ruling Justice and Development Party (AKP) lost its majority.
The AKP and main opposition Republican People's Party (CHP) on Monday held a fifth and final day of talks on a possible grand coalition.
But there was no immediate hint of a breakthrough with both sides saying they would first report to their party leaders.
AFP contributed to this report.