Hundreds of Syria’s Kurdish population have died in clashes in north-eastern Syria with Islamic factions armed and financed by Turkey, Saudi Arabia and Qatar, with US support.

The fighting between the Kurds and the Islamists adds another layer of conflict to the proxy war to unseat President Bashar al-Assad. Fighting within the anti-Assad opposition has already set the so-called Free Syrian Army (FSA) against Jihadist groups such as the Al Nusra Front and Islamic State of Iraq and Levant (ISIS).

It testifies to the reactionary character of the US campaign for regime change in Syria, which has seen sectarian fighting and bombings spread throughout the region. The Kurdish conflict in particular threatens to unleash fighting inside Turkey and in the oil-rich semi-autonomous Kurdish Regional Government in Iraq.

While there has been sporadic fighting between the Kurds and FSA/Islamists over the last two years, the Kurds have generally tried to avoid conflict with either government or opposition forces. The spark for the recent fighting was an attack last month on a group of Kurdish women fighters by the al-Nusra Front in Hassakeh province, in north-east Syria.

The opposition forces, made up of the Free Syrian Army (FSA) and various Islamist groups, have carved out a mini-Islamic state in the Euphrates valley stretching from the Turkish border, through the eastern part of Aleppo, Raqqah, the oil-rich region around Deir el-Zour, as far as Iraq, where they have instituted a reign of terror. They are seeking to extend their control further east to the oil-producing region held by the Kurds.

The People’s Defence Units (YPG), the armed wing of the dominant Kurdish group, the Democratic Union Party (PYD), responded by driving the Islamists out of Ras al-Ain and taking control of a border crossing with Turkey’s south east, predominantly Kurdish region. The PYD is affiliated to Turkey’s Kurdistan Workers Party (PKK), which seeks Kurdish autonomy.

In the fighting Islamists killed hundreds of Kurdish civilians in the towns of Tal Aran and Tal Hasel, south-east of Aleppo, and a prominent Kurdish politician, Isa Huso. The attacks were so egregious that the Obama administration felt obliged to join Russia in condemning them.

The fighting has forced tens of thousands of Kurds to flee across the border into Iraqi Kurdistan. The Turkish border is much closer, but this has been sealed in what is effectively a blockade, both to support the Islamists and to avoid any increase in the number of Kurds living within Turkey.

The PYD has accused Ankara of arming the Islamists against them. Some 150,000 Syrian refugees are already registered in Iraq where the Kurdistan regional government and relief organisations are struggling to cope.

The president of Iraq’s Kurdistan Regional Government, Massoud Barzani has sought to avoid being drawn into the civil war in Syria while increasing trade and oil exports to Turkey. He threatened to intervene to defend Syria’s Kurdish population.

In July 2012, the Assad regime withdrew its forces from the predominantly Kurdish areas in northern Syria, adjacent to its borders with Turkey, Iran and Iraq, also home to significant Kurdish minorities, in the hope of neutralising the Kurds in the conflict.

The PYD has largely assumed control of the region, carving out semi-autonomous territories.

Syria is gradually breaking into three, a result favourable to the Western powers. Last month, the PYD announced a constitution and a plan to elect a council to administer the area which it calls Rojava, or West Kurdistan, although it has been anxious to reassure Turkey that this is only a temporary set up pending the resolution of the conflict in Syria.

The Kurds are the largest ethnic minority in Syria, about ten percent of the population, with most living in the north east, although significant numbers also live in Aleppo province and other parts of the country. Hostile to the Assad regime, which has long subjected the Kurdish population to political and cultural repression, including the denial of citizenship to hundreds of thousands following the 1962 census, the Syrian Kurds also face Western-backed forces pursuing a sectarian and Sunni Islamist agenda. This is driven in significant measure by foreign fighters and large amounts of Saudi and Qatari arms and aid.

Turkey plays host to and arms and trains the anti-Assad insurgents. The Islamist government of Recep Tayyip Erdogan was the most aggressive in calling for “regime change” in Syria and the prime mover in organising the military build-up against Syria in 2011. It has massed tanks and warplanes on its border and carried out artillery barrages against Syrian targets in retaliation for any stray rounds that crossed the Turkish border.

Of great concern to Erdogan is the impact of the Syrian Kurdish- Islamist clashes on the domestic situation in Turkey, where his government’s role in the Syrian conflict is deeply unpopular—particularly following two bombings, assumed to be by al-Nusra Front, that killed at least 51 people and injured 140 last May in Reyhanli, near the Syrian border which the Syrian opposition forces use as their base.

The clashes also threaten the talks with Turkey’s Kurdish leaders, begun following jailed PKK leader Abdullah Ocalan’s announcement of a ceasefire after months of talks with the intelligence forces in March.

Erdogan has sought to negotiate a peace deal with the Kurdish separatist forces and then use them to further his war aims in Syria. But there were also important domestic considerations. The support of the Kurdish Peace and Democratic Party (BDP), which is close to the PKK and has several MPs in the Turkish parliament and many of the mayors in the predominantly Kurdish southeast of the country, and their “left” hangers-on would provide him with additional support in his attacks on the working class.

It would aid his attempts to amend the constitution in favour of an executive presidency, for which he would run in 2015 when his maximum period in the premiership expires. A more authoritarian presidential system is important for Erdogan as a means of curbing the power of the army, which has organised repeated coups in 1960, 1971, 1980 and the 1997 “soft coup” against the government of the AKP’s forerunner, the Islamist Welfare Party.

Erdogan was enraged by Washington and the regional Sunni powers’ backing for the military coup against the elected Muslim Brotherhood government of President Mohamed Mursi. He is determined to neutralise the Turkish army as an independent power factor.

The long prison terms handed down to hundreds of top army officers, officials and journalists in the Ergenekon trial earlier this month for plotting coups against the Erdogan government, killings and paramilitary operations were aimed at reining in the army and strengthening popular hostility to it.

But Erdogan faces bitter opposition to any deal with the Kurdish separatist forces, which is why the promises of a reform package and the release of Kurdish political prisoners have yet to materialise. Without any concessions before Kurdish National Congress, due to take place in Erbil on August 24 with delegations from Turkey, Syria, Iraq and Iran, the PKK has indicated its willingness to take up arms again.