Kurdish fighters in northern Syria today accused Turkish troops of shelling their positions after a weekend of unrest that dented chances of peace with Turkey's own long-suppressed Kurdish population.

The Kurdish People's Protection Units (YPG) said on Monday that Turkish tanks had fired on both it and allied Free Syria Army (FSA) rebels in a village close to the Islamic State (IS) held town of Jarabulus on Friday, injuring four FSA members and a number of civilians.

It added that Turkish forces targeted on the same village on Sunday, as well as a YPG vehicle east of the border enclave of Kobane. The YPG are fierce opponents of IS and receive regular US air support in their fight against the extremists, but Turkish leaders have described the group as "terrorists" due to its affiliation with the banned Turkish Kurdistan Workers' Party (PKK).

"Instead of targeting IS terrorists' occupied positions, Turkish forces attack our defenders positions," the YPG said in a statement. "This is not the right attitude. We urge Turkish leadership to halt this aggression and to follow international guidelines. We are telling the Turkish Army to stop shooting at our fighters and their positions."

A Turkish official told Reuters that they were investigating the claims, and that the YPG had not been intentionally targeted.

"The ongoing military operation seeks to neutralize imminent threats to Turkey's national security and continues to target Islamic State in Syria and the PKK in Iraq... The PYD, along with others, remains outside the scope of the current military effort," the official said, referring to the YPG's political arm.

The incident came amid heightened tensions as Ankara continued to bomb PKK bases in northern Iraq, and three members of the country's security forces were killed over the weekend.

Protesters scatter after hitting a police vehicle with a Molotov cocktail during clashes in Istanbul's Gazi neighborhood on Sunday. Photo by John Beck.

Turkey launched a two-pronged "war on terror" last week, bombing IS in Syria on Friday after the jihadists fired on a Turkish border post the previous day, killing one soldier and prompting a brief skirmish that also left at least one IS fighter dead.

But its attack jets also pounded PKK strongholds in northern Iraq's Qandil mountains, in what is the most intensive campaign against the group there since 2011. Strikes continued on Sunday as Turkish F-16s based in southeastern Diyarbakir bombed PKK positions in Hakuk, northern Iraq, according to a number of local media outlets.

Turkey, as well as the US and the European Union, view the PKK as a terrorist organization due to a history of attacks on civilian and military targets during a 30-year fight for autonomy from the Turkish state that claimed more than 40,000 lives. Its members are also fighting IS in Kurdish Iraq alongside the regional government's Western-backed peshmerga forces.

A landmark ceasefire agreement brought a fragile peace to Turkey's majority Kurdish southeast, granting more rights to the Kurdish population, long subject to restrictions on use of its own language and cultural practices.

But the deal had shown signs of strain in recent months as President Recep Tayyip Erdogan increased nationalistic rhetoric in the leadup to June's parliamentary elections and frustration built among Kurds at perceived government inaction regarding peace processes.

On Saturday in response to the airstrikes the PKK said that conditions were no longer in place to adhere to the ceasefire. A car bombing in the town of Lice in Diyarbakir province killed two soldiers and injured four late the same day as a vehicle traveled to disperse Kurds who had blocked an intersection.

A statement issued by the provincial governor's office the following day blamed "terrorists" for the attack, a term usually used to refer to the PKK. No group has yet claimed responsibility.

"By carrying out the recent attacks Turkey has practically and unilaterally ended the state of non-conflict and the peace-process," Zagros Hiwa, a spokesman for the PKK's executive political council, the Kurdistan Communities Union told VICE News.

"As the Kurdish Freedom Movement we will defend ourselves and our peoples against the attacks of Erdogan Administration. A new era of struggle and resistance has started for the Kurds."

A masked protester runs through crowds of tear gas during clashes in Istanbul's Gazi neighborhood on Sunday. Photo by John Beck.

Anti-government groups had planned to hold a peace rally in Istanbul on Sunday in response to the Iraqi airstrikes. But authorities banned the gathering, claiming that it would be used for "provocative" acts by groups including the PKK and disrupt traffic. Instead, organizers read a brief statement to some hundreds gathered at the planned starting point before dispersing peacefully.

Meanwhile, in the city's Gazi neighborhood, a police officer was killed during clashes with demonstrators sparked by the death of a woman who died during a security crackdown on Friday. State media and officials described her as dying during in a gunfight with police.

The state-run Anadolu Agency reported that the officer was fatally shot while entering a building to arrest protesters.

The two sides battled each other for most of Sunday. Groups of masked youths, including members of the Marxist-Leninist Revolutionary People's Liberation Party-Front (DHKP-C) and others wearing Kurdish colors, built barricades across many of the district's central junctions.

Police attempted to disperse the protesters with tear gas, water cannon, and armored vehicles, while demonstrators responded by throwing stones and the occasional Molotov cocktail. By evening a number of flaming barricades were still blocking roads, while acrid clouds of tear gas hung over several blocks as local residents caught in the running fighting took shelter in supermarkets and cafes. Others cheered on protesters from their windows, rattling pots and pans in a symbol of defiance.

A masked protester in front of a burning barricade during clashes in Istanbul's Gazi neighborhood on Sunday. Photo by John Beck.

The strikes on IS mark a significant policy shift for Turkey, which is a member of the US-led coalition that has been bombing the group in Iraq and Syria since last year, but it had not taken on a prominent role, despite intense international pressure and criticism. Instead, IS had been able to bring weapons and fighters into its territory through Turkey and smuggle oil out on a fairly large scale, Turkey has since tightened security and detained hundreds of IS suspects, officials say.

Ankara also decided this week to allow American jets to conduct operations from its southern Incirlik airbase, a move that would enable the US to intensify its air campaign against IS in Syria by moving its base of operations far closer. On Sunday, Ankara requested a meeting of NATO's North Atlantic Council to discuss its airstrikes on both IS and the PKK, as well as threats against its own security.

Turkey has become increasingly enmeshed in the fight against IS. A suicide bombing carried out by a Turkish citizen suspected of links with the extremist group killed 32 people in Suruc, a small town in Sanliurfa province on the border with Syria on June 27, an attack widely viewed as being at least partly motivated by the crackdown against IS.

It targeted a pro-Kurdish socialist youth group, however, and led many Kurds, including political figures, to accuse Anakara of supporting IS and allowing it to freely operate inside Turkey. Two police officers were also found shot dead nearby on Wednesday. The PKK subsequently claimed responsibility, claiming the men were IS collaborators.

Allegations of Turkish support for IS have also been repeated by members of the pro-Kurdish People's Democratic Party (HDP), which secured a place in parliament for the first time by passing the crucial 10 percent vote threshold in June's elections.

A Kurdish protester with a handful of stones ready to throw at police during clashes in Istanbul's Gazi neighborhood on Sunday. Photo by John Beck.

In the process it deprived Erdogan's ruling AKP of an overall majority for the first time since it came to power in 2002, and blocked the president's dreams of changing the constitution to a presidential system in order to boost his dominance of Turkish politics. The AKP will now have to form a coalition government or stage snap elections, and some opponents have alleged that the war on terror is designed to boost its appeal to nationalists and divert attention from internal failings should the latter scenario play out.

HDP co-chairman Seahattin Demirtas alleged last week that the AKP had backed the Suruc bombing in order to cause violence in Turkey and improve its own lot in the next round of voting.

As part of the recent security campaign, Turkish police also carried out a series of raids on "terror organizations" that Prime Minister Ahmet Davutoglu said led to the arrest of 590 people. IS suspects were targeted alongside the PKK and DHKP-C. HDP members were also reportedly detained, however, leading to a sense among some Kurds that the targeting of IS is being used as an excuse to renew a crackdown on them, further imperiling the peace process.

Hiwa said that Turkey's intervention against IS was a tool aimed at lending legitimacy to a crackdown on Kurds and pro-Kurdish Turks after Erdogan's presidential ambitions were blocked by the HDP. "Turkey now is fighting the Kurds and the PKK under the cover of 'fighting terrorism.' Carrying out minor attacks on some so-called ISIL positions in Syria are only a disguise for Erdogan's attacks on the Kurds."

He added that he believed this was a reformulation of AKP pre-election plans to launch strikes on PKK positions in Iraq.

Tear gas in the streets of Istanbul's Gazi neighborhood on Sunday. Photo by John Beck

The international community has appealed for calm. Brett McGurk, US envoy to the anti-IS coalition welcomed the decision to attack the extremist group, saying, "We look forward to intensifying cooperation with Turkey and all of our partners in the global fight against ISIL [IS]," in a tweet. He went on to condemn PKK attacks, but noted that there was was "no connection" between Ankara's crackdown on the group and the strengthened cooperation against IS.

Others also backed Ankara's security efforts, but urged officials to preserve the Kurdish peace process. European Union foreign policy chief, Federica Mogherini, said it should be kept "alive and on track" in a telephone conversation with Turkish Foreign Minister Mevlut Cavusoglu. Meanwhile, German Chancellor Angela Merkel expressed solidarity with "the fight against terrorism", in a call with Davutoglu, but appealed on Turkey "not to give up the peace process with the Kurds, but to stick to it despite all the difficulties," according to a statement.

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