The PKK, which seeks autonomy for parts of southern Turkey, is designated a terrorist group by the United Nations, the European Union and several other nations.
After a March 2013 ceasefire, there was hope that the 30-year war might be wrapping up, especially as the PKK's Syrian affiliate in mid-2014 started playing a key role in taking on so-called Islamic State (ISIS) in Syria.
However, Turkey’s bombing of PKK bases in northern Iraq in July – after the rebels killed two policemen – reignited the conflict. The level of violence remained relatively limited until bombs planted by the rebels destroyed two military vehicles and killed 16 Turkish soldiers on Sunday. After one of the deadliest PKK attacks ever, Turkish Prime Minister Ahmet Davutoglu pledged to "wipe out" the rebels, who responded two days later by bombing a minibus in eastern Igdir, killing 14 police.
Metin Gurcan, a former member of the Turkish special forces and now an analyst tracking the conflict, reckoned the PKK attacks were calculated to increase the intensity of the conflict.
“These attacks are likely a critical juncture… they could be a game-changer,” he told IRIN. “The PKK has deliberately elevated the conflict to a new level.”
Here are three ways in which this conflict could have major implications for both Turkey and the region.
1. The domestic sphere
There is likely to be a major impact on Turkey’s upcoming elections, which are taking place just three months after an inconclusive poll result left the parties unable to form a coalition.
The result was a major shock for President Recep Tayyip Erdogan and his AKP party, which has held a majority since 2002 but is now forced to seek cohabitation with minor parties.
The opposition newspaper Today’s Zaman suggested on Monday that the election might be postponed in parts of the country, particularly in the southeast where violence has been most intense.
“One risk that we have been talking about, and there is a lot of speculation about, is a situation where the intensification [of the conflict] compromises the prospects of free and fair elections,” Turkey analyst at the IHS think tank Ege Seckin told IRIN.
“The government is arguing that the PKK is putting pressure on the local population and thereby affecting the way they vote,” Seckin said. “From the opposition’s perspective any delay would be in line with the government’s interests. Erdogan knows he doesn’t stand a chance of getting a lot of votes from these [predominantly] Kurdish areas."
The most likely loser from any delay is expected to be the People’s Democratic Party (HDP), which is supported by a mixture of Kurdish groups and Turkish liberals. It gained seats at the last election for the first time after winning almost 13 percent of the vote.
2. Regional impact
After today’s bombing, Turkish troops followed the retreating PKK fighters back inside Iraq. “This is the kind of operation that the Turkish military conducts in order to prevent armed fighters from escaping after an attack,” said a Turkish government spokesman, who asked to remain anonymous in line with government protocol. “In response, Turkish troops crossed the border to target the remaining [PKK] members.”
That part of Iraq is governed by the semi-autonomous Kurdish Regional Government (KRG), which has good relations with Turkey and a fractured relationship with the PKK. Nevertheless, KRG President Massoud Barzani has repeatedly called for Turkey to stop bombing inside Iraq.
The government spokesperson said the ground incursion was authorised by the Turkish parliament, but it was unclear whether the KRG had given permission to Ankara or indeed was notified in advance.
“Barzani is under heavy pressure to voice a bit more opposition to what Turkey is doing,” Seckin said.
Likewise, Turkey is also carrying out attacks against ISIS inside Syria, so an all-out conflict with the PKK could weaken the country’s ability to tackle the Islamist militants.
3. The human toll
The impact on communities in both northern Iraq and southern Turkey has yet to be properly assessed but there have already been allegations of civilian deaths caused by the airstrikes.
Since Friday, the main border crossing between Iraqi Kurdistan and Turkey has also been closed, cutting off the vital trade link across the frontier.
There are also a number of camps for displaced Iraqis near the border, while the United Nations uses the route to bring food to its extensive programmes inside Iraq. A long-term closure would make it difficult for the United Nations and humanitarian organisations to continue to provide for those in need.
Seckin said the fact that Iraqi Kurdistan doesn’t have an alternative route to the global markets makes the border crossing an even greater potential flashpoint. Turkey’s control over the border is seen as wielding economic power over Iraq’s Kurdish region.