As Turkey's Erdogan cracks down on internal dissent, Syrian Kurds, viciously opposed to Turkey-backed terrorist rebel groups, may provide the most potent challenge yet for the Turkish president.

The US-backed Syrian Democratic Forces (SDF), began multiple offensives against the al-Nusra Front and its US-backed Free Syrian Army (FSA) allies over the weekend, reports on both sides' social media and YouTube accounts suggest.

It is unclear if the SDF attacked the al-Nusra Front and its allied FSA units in coordination with previously reported Russian bombings of al-Nusra Front targets in Syria's northern Aleppo region.

On November 25, a day after Turkey shot down the Russian plane, the co-head of Syria's Democratic Union Party (PYD) Salih Muslim told Sputnik that the party seeks cooperation with Russia.

The PYD also has an armed wing, the People's Protection Units (YPG), which is said to form the backbone of the SDF.

"Until now we have not had the opportunity to establish active cooperation with Russia, but we would be glad if such an opportunity arose. Russia has not approached our region very closely yet, it is active in the West. I believe that in the future we will be able to establish dialogue on military cooperation with the Russian side," Salih Muslim said.

Russian President Vladimir Putin told French President Francois Hollande on November 26 that Russia is ready to work with the US-led coalition against Daesh, also known as ISIL, although he did not make it clear if the cooperation would include Syria's Kurds and the SDF.

Aggression between the al-Nusra Front, its FSA allies and the SDF erupted in the suburbs of Aleppo over the weekend, which al-Nusra declared a "war zone" after a prolonged armed neutrality agreement.

"In the midday hours of November 26, terrorist groups affiliated to the Al-Nusra Front – using heavy weapons – carried out an attack on the Sheikh Maqsoud neighborhood in Aleppo. The Defense Units there managed to conduct an appropriate response to repel the terrorists’ efforts," the YPG said in a statement posted on its official Facebook page.

Turkey's shootdown of the Russian plane on November 24 could be an indication not of NATO aggressiveness or Erdogan's personal madness, but the beginning of a civil war in Turkey.

US-Backed, Pro-Russian?

The Syrian Democratic Forces (SDF) are a US-backed group of Arab, Kurdish and Assyrian fighters. The previous incarnation of the group, a YPG-FSA unified command known as Euphrates Volcano, praised Russian airstrikes and requested arms to fight Daesh, also known as ISIL.

The YPG is considered an offshoot of the Kurdistan Workers' Party (PKK), which is banned in Turkey as a "terrorist" organization. It considers Abdullah Ocalan, imprisoned in Turkey, its ideological leader.

After the shootdown of the Russian plane on November 24, the YPG warned that it would shoot down all Turkish warplanes and helicopters which breached its territory.

"We the People's Defense Units (YPG) warn against these irresponsible actions, in case of repetition, we will conduct the necessary response to target any violations of this kind," the YPG said on November 25.

© AP Photo / IHA agency Turkish Police Fire Tear Gas, Use Water Cannon Amid Protests Over Murder of Kurdish Lawyer (VIDEO) At around the same time, the PKK in Turkey began to launch attacks on soldiers and policemen stationed along the border with Syria.

Edging Toward Civil Strife

Turkey is reportedly pulling troops and equipment including tanks toward the Syrian border while cracking down on internal dissent by Kurdish groups.

Turkish military helicopters reportedly shelled Kurdish areas on the Turkish side of the Syrian border, while the military declared curfews in other areas, according to Reuters.

The moves come after both tensions over Syria's conflict and the murder of a prominent Kurdish activist, Tahir Elci, which the country's pro-Kurdish HDP party called a "planned assassination." Prior to the assassination, Elci called for the Kurdistan Workers' Party (PKK) to be taken off Turkey's "terrorist" list.

Turkey has also jailed journalists from the country's opposition Cumhuriyet newspaper, which revealed Turkish arms shipments to Syrian rebels in May.

Would Russia Act?

Although many voices in Russia have called for support of Kurds against Turkey, it remains a difficult issue for policymakers. Russia itself has few interests with Kurdish movements, as they often support competing interests.

In the case of Syria's PYD and its YPG militia, the group maintains a difficult neutrality with the Syrian government. While Russian President Vladimir Putin has pushed Syrian President Bashar Assad to work with Kurdish groups, and Assad reacted "positively," disagreements remain, which appear unlikely to be solved without comprehensive peace talks within Syria.

At the same time, reaching hasty agreements without definite terms could lead to difficulties for both parties.

Russia has recently said that it would act to close the Syrian border with Turkey, which is currently accessible to both Turkish-backed FSA/al-Nusra rebels and Daesh, to choke off the groups' supply routes.

At the same time, the SDF seeks to go south toward Raqqa before closing off the group's Turkish supplies. The arrival of 50 US Army Special Forces troops in Kobane (Ayn al-Arab) appears to suggest this. Without any sort of agreement, however, Syria risks becoming a five-sided conflict with the government, Kurds, the US, Turkish-backed rebels and ISIL — all sides with competing interests.

The views and opinions expressed in the article do not necessarily reflect those of Sputnik.