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.

Three 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 (IS) militants in Syria and PKK rebels in northern Iraq. But so far the raids have overwhelmingly targeted the Kurdish rebels.

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.

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 destabilise the region".

In Washington, State Department spokesman Mark Toner told reporters Ankara had a right to defend itself 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.

- 'Three 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 IS.

The PKK, which accuses the government of collaborating with IS, shot dead two Turkish police in reprisal, starting a wave of violence that has shattered a 2013 ceasefire.

President Recep Tayyip Erdogan, who opponents accuse of orchestrating the crisis to boost his popularity, 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, the army said.

Later on Tuesday, one soldier was killed and another injured when Kurdish militants attacked with missiles an armoured brigade in the Silopi district of Sirnak, security sources said.

Militants on motorbikes also attacked a police headquarters with rocket launchers in Hakkari province without causing any casualties, the Anatolia news agency said.

Turkish F-16s bombed PKK targets around the district of Daglica in southeastern Turkey -- long seen as a PKK stronghold -- as a reprisal for a mortar attack earlier in the region that lightly wounded a six-year-old girl, the Dogan news agency said.

According to an AFP toll, 20 members of the Turkish security forces have been killed in attacks blamed on the PKK since the current crisis began.

- 'Armed drones use Incirlik' -

Meanwhile, Turkey's Western allies are also waiting for it to commence full-scale operations against IS 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 IS 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.

"This weekend, the United States did begin flying unmanned, armed counter-ISIL missions from Turkey," said Pentagon spokesman Jeff Davis, using a variant name for IS.

"Just a start..." tweeted the US deputy special envoy for operations against IS, Brett McGurk.

Dozens of piloted US jets are expected to arrive in the next days to ramp up the bombing raids, Turkish media have reported.

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.