Ankara, Washington’s NATO ally, continued launching airstrikes in northeast Syria on Monday against US-backed Kurdish militias. According to the UK-based Syrian Observatory for Human Rights, at least 20 people were killed and dozens more were wounded.

Turkey’s latest air campaign against the armed Kurdish groups in US-occupied Syria, as well as northern Iraq, began on Thursday. It was precipitated by a recent suicide bombing which targeted the Turkish Interior Ministry. The Kurdistan Workers’ Party (PKK) claimed credit for the attack, both Ankara and Washington have deemed the group a terrorist organization.

Turkey insists the suicide bombers entered the country by way of Syria, although the Syrian Democratic Forces (SDF) denies this is the case. The SDF, Washington’s proxy in its years-long illegal occupation of roughly a third of Syria, is dominated by the Kurdish YPG which Ankara sees as ancillary to the PKK. The US has about 900 troops in northeast Syria, controlling most of the country’s oil and wheat resources as an extension of Washington’s economic war against Damascus. Additionally, thousands of Turkish troops are occupying areas in northern Syria.

Monday’s strikes hit an SDF training center in Al-Malikiyah, a small city in the northern countryside of Al Hasakah province. The SDF stated “a number of our forces were killed and others wounded.” On Friday, Ankara claimed to have bombed 30 sites in Syria used by the PKK. Nearly 60 Kurdish militants were killed in overnight assaults on Saturday, according to Turkey’s Defense Ministry.

Last week, Turkish Foreign Minister Hakan Fidan declared “All infrastructure, superstructure and energy facilities that belong to the PKK and the YPG, especially in Iraq and Syria, are legitimate targets of our security forces, armed forces and intelligence units from now on.”

On Thursday, an American F-16 shot down a Turkish drone operating near US forces. While Turkey and the US are at odds over the SDF, both sides ultimately played down the incident with the Pentagon saying they do not believe the drone was targeting US troops. Ankara blamed the NATO-on-NATO clash on a miscommunication in the “deconflicting mechanism.”

This comes as Arab tribesman living in US occupied territory are revolting against Kurdish rule. This has led to fighting which saw more than 100 people killed and thousands displaced during recent months. Some analysts have argued the ethnic tensions boiling over into a guerilla war may render the US occupation untenable.

Washington maintains that its unwanted presence in Syria is aimed at ensuring that the Islamic State (IS) is defeated. But IS took over large swathes of eastern Syria and western Iraq as a result of a failed regime change operation which saw the CIA, Turkey, Israel, Saudi Arabia, and other US allies, arming and funding rebel groups including al Qaeda affiliates.

The proxy war killed hundreds of thousands of people but ultimately failed in its attempt to overthrow the Syrian government. The terrorist group has been all but destroyed by Damascus with its Russian and Iranian allies.