Turkey has expressed alarm over the intensifying clashes between the Islamic State of Iraq and al-Sham (ISIS) and the Syrian Kurdish Democratic Union Party's (PYD) People's Protection Units (YPG) on its doorstep, and has tightened security measures against any threat that might penetrate its territory. To this end, Ankara has changed its rules of engagement for the second time regarding Syria to be able to fight against the whopping threat of ISIS, which captured large swathes of territory in Syria and Iraq. According to the new changes to the scope of Turkey's military operation in Syria, Turkey will see any armed element that approaches its frontier, not least ISIS, and will strike for self-protection.Turkey's rules of engagement, which previously only targeted Syrian President Bashar Assad's regime, will become more comprehensive and include ISIS in its amended form. The implementation of the regulation in military intervention in Syria is expected to be put into effect this week without losing time as Ankara's concerns are at their peak that the violence in Syria could extend to Turkey and lead to a costly protracted refugee situation in the country.Turkey changed its rules on border engagement on June 22, 2013 when a Turkish jet was shot down over the southern Mediterranean.On June 26, 2013, then Prime Minister Recep Tayyip Erdoğan announced that Turkey's rules of engagement had changed. In accordance with the new rules, all Syrian military units approaching the border would be declared a threat and a military target even if they do not cross the border and Syrian military units could still be subject to an attack by Turkey, deeming them a security threat and hostile.ISIS along with other armed groups that have the potential to jeopardize Turkey's security will be included as threats to Turkey in the amended rules and the Turkish Armed Forces could launch an operation against ISIS once it approaches its borders.Meanwhile, interim Prime Minister Ahmet Davutoğlu has given orders to the Turkish Army to prepare for an operation against ISIS in northern Syria in a written instruction. The Malatya 2nd Army Command is expected to lead the operation in case of a cross-border campaign. It has also been discovered that the Air Force is on patrol to keep tabs on ISIS positions close to the border.Intense security precautions have been adopted after ISIS militants disguised in YPG uniforms advanced into the Syrian Kurdish border town of Kobani on Thursday and carried out a fierce attack on the town which is currently under the protection of the YPG.The attacks were launched at three different points, killing at least 146 people and leaving 100 others wounded in five explosions according to an activist monitoring group, making it the second-biggest massacre in Syria.Turkey's concerns about instabilty in the region is not limited to ISIS. The take-over of Tal Abyad from ISIS by PYD forces also became a matter of unsettlement for Turkey. Tal Abyad lies between two Kurdish-controlled cantons, Kobani and Jazeera, so its capture is of strategic importance as it opens a supply route between the two spots, triggering Turkish fears that such bridging will ramp up Kurdish power in the region, ultimately posing a threat to the security of the Turkish territory. President Recep Tayyip Erdoğan previously said he was worried that the PYD and PKK were filling the vacuum left behind after ISIS receded, and that it could "create a structure" near its borders that might threaten the country.He said on Friday that Turkey will not allow a new state to be founded in northern Syria. Erdoğan said that it was clear that Bashar Assad, ISIS, PYD and the outlawed PKK are in some sort of cooperation."I underline Turkey's stance once again, we will not allow a state to be established in northern Syria." Erdoğan said. He also slammed allegations associating Turkey with terrorist groups, amid renewed fighting between Kurdish forces and ISIS militants in the Syrian town of Kobani near the Turkish border."I am calling on those who have been tweeting 'Terrorist Turkey,' " he said, "How dare you define a country that has provided shelter for Kobani residents as a terrorist country."The President noted Turkey supports the fight for freedom in Syria, "but we never act in unison with terrorist groups.""Nobody can associate Turkey with the Assad regime, a state terrorizing its people or with other terror groups," he added.