US - led coalition warplanes have inflicted a missile strike on a camp of Syrian regular troops in the Dier al Zor province, killing three soldiers. Damascus has slammed the incident as an “act of aggression. ” This is the first time coalition planes have hit Syrian troops. The Syrian government has confirmed that there are three casualties and 13 personnel injured, as well as a number of military vehicles destroyed. The coalition jets fired nine missiles at an army camp in the Dier al Zor province, which remains mostly under the control of Islamic State. The incident is the first of its kind since the coalition started to bomb Syrian territory more than a year ago. The Dier al Zor province is eastern Syria, and is largely controlled by Islamic State (formerly ISIS/ISIL). The region is of extreme strategic importance to the terrorist group, as it contains a number of oilfields, which are a major source of revenue for ISIS. On November 24, a Turkish Air Force F-16 jet shot down a Russian Su-24 bomber over Syria. Ankara claims the Russian plane briefly crossed into Turkish airspace. One of the Russian pilots was killed by Syrian rebels as he ejected from the stricken plane, while the other was rescued in a swift operation during which one Russian serviceman was killed. The downing of the bomber by Turkey came after a successful Russian bombing campaign against ISIS oil infrastructure on the Syria-Turkish border, and was seen as revenge. Putin described the act as "a stab in the back" and accused Erdogan of benefiting from the illegal oil trade with ISIS and financing the terrorists. Russia has been conducting airstrikes targeting Islamic State (former ISIS, ISIL) and other terrorist groups in Syria since September 30. The strikes were launched after a formal request from Damascus. Russian jets have been carrying out sorties from Moscow’s Khmeimim Air Base in Latakia. The US-led coalition’s airstrikes in Syria are in fact illegal, as it has never received permission from Syrian President Bashar Assad to enter the country’s airspace. In response to the UK’s decision to join the bombing campaign in Syria, President Assad reiterated in an interview with the Sunday Times that the presence of Britain in Syria is unlawful as neither Damascus nor the United Nations have given London the green light to bomb Syrian territory. “It will be harmful and illegal and it will support terrorism, as happened after the coalition started its operation a year or so [ago], because this is like a cancer,” Assad said.