Not far from the Turkish border with Syria, another war is raging.

In the heart of the ancient city of Diyarbakir, behind its historic black-stone walls, security forces have been engaged for weeks in clashes with the youth wing of an outlawed Kurdish separatist group. Whole neighborhoods have been sealed off under curfew; tens of thousands of people have been forced to flee.

The mini-rebellion has been echoed elsewhere in Turkey's restive southeast, a region that is home to a majority Kurdish population and that has been in the grips of a low-level civil war since tensions flared last summer. The violence is likely the worst seen in the past two decades.

The Turkish government claims more than 200 policemen and soldiers have been killed since July, while some estimates place the local civilian death toll around that number as well. The Turkish crackdown on the militants — fighters belonging to the banned Kurdistan Workers' Party, or PKK — has led to more than 500 guerrilla deaths.

There's little indication of the hostilities calming. Since a peace process between the two sides fully collapsed last year, separatist-minded Kurds in a number of towns and neighborhoods pushed for de facto autonomy. The predominantly Kurdish border town of Cizre has been a hotbed of unrest and resistance for more than a year now and is now in the midst of an intense Turkish military clampdown.

Rights groups and critics of the Turkish government accuse the state of denying civilians stuck in the siege adequate access to medical care. On Tuesday, the top human rights official at the United Nations also urged Ankara to investigate an incident that occurred last month, which involved the apparent shooting of unarmed civilians, leading to a number of casualties.

Video footage appeared to show a group of civilians moving in front of an armored military vehicle before they "were cut down by a hail of gunfire," said Zeid Raad al-Hussein, the U.N. high commissioner for human rights.

Turkish authorities have previously rejected claims that their security forces were impeding aid to civilians. "They are deliberately not bringing the wounded out," said Turkish President Recep Tayyip Erdogan, referring to the Kurdish militants holed up in parts of Cizre and other towns in Turkey's southeast.

The PKK's insurgency has blown hot and cold since the early 1980s. It has led to some 40,000 deaths in those years. Under the rule of Erdogan and his Justice and Development Party, some of the causes for Kurdish grievance — including the suppression even of the use of their own language — started to be addressed. But the shadow of the Syrian war has led to a profound unraveling.

As WorldViews noted earlier, the territorial gains made by Syrian Kurdish militias over the past two years had ripple effects across the border. The Turkish government, which has spent decades attempting to subdue Kurdish separatist ambitions, looked on with horror as the PYD, a Syrian Kurdish faction historically linked to the PKK, emerged as a key player in northern Syria. The PYD's role on the front lines of the war against the Islamic State endeared it to the West, including the United States, which gave it aid.

"Ankara’s real fear is that the PYD’s success in Syria will dangerously strengthen the PKK in its fight against Turkey," writes Nicholas Danforth, a Turkey scholar at the Bipartisan Policy Center. "For Washington, by contrast, the PYD’s military success confronting [the Islamic State] in Syria remains the group’s main appeal."

This tension is playing out in the current, fitful round of U.N.-brokered talks over the Syrian conflict in Geneva. Turkey insisted that the PYD not be extended an invitation; the United States, an increasingly grudging ally, acquiesced. Russia, whose military intervention on behalf of the regime of Syrian President Bashar al-Assad infuriated Turkey, is now also opportunistically cozying up to the Syrian Kurds. It had earlier demanded the PYD be included in the talks.

Ankara casts the PYD as a stooge agent of the Assad regime; the PYD, meanwhile, accuses Turkey of aiding the Islamic State in order to undermine the prospect of an autonomous Kurdish state along its border.

Within Turkey, criticism of the government's actions has led to harsh punishments. Turkish prosecutors are currently seeking life sentences for two prominent journalists who published a story that linked the Turkish government to arms shipments sent to Syrian rebel factions across the border. In a wholly separate case, an academic at a university in Ankara faces seven years jail time for simply circulating an exam question that involved the writings of the PKK's jailed leader, Abdullah Ocalan.

The escalation of violence and instability in the region has grave consequences for larger crises currently vexing the international community.

"Turkey's domestic peace is not an issue for Turkey alone," Selahattin Demirtas, a leading opposition politician and co-leader of the Peoples' Democratic Party, a leftist, pro-Kurdish party, told reporters in Brussels last week. "It is directly related to the resolution of the Syrian conflict and to the migration problem in Europe."

All the while, resentment and anger is festering on the streets of Diyarbakir and other majority Kurdish cities. The city boasts a huge cemetery for Kurdish youth who have gone off to fight across the border in Syria. A radicalization has set in.

"Many residents of these towns are poor families who were forced to flee the countryside when the conflict between the Kurds and the Turkish state was at its peak in the 1990s," writes Abdullah Demirbas, a former mayor of Sur, the old quarter in Diyarbakir that's now the epicenter of clashes. "Those who are digging trenches and declaring 'self-rule' in Sur and other cities and towns of southeastern Turkey today are mostly Kurdish youths in their teens and 20s who were born into that earlier era of violence, poverty and displacement, and grew up in radicalized ghettos."

Demirbas, a controversial figure in his own right, has seen one of his own sons join the PKK.

"Now a new generation will grow up with the trauma of killing, destruction and forced migration," he writes. "Where will they go? What will become of them?"