Turkey strikes targets in Syria in retaliation for shelling deaths Smoke rises after shells landed Wednesday in Akcakale, a town in southeastern Turkey's Urfa province. NEW: No evidence of broader conflict, U.S. defense official says NEW: NATO council is meeting on the situation Turkey strikes targets in Syria following shelling of a Turkish border town Akcakale "was hit by artillery fire belonging to the Syrian regime forces," Turkey says (CNN) -- Turkey fired on targets in Syria in response to the shelling of a Turkish border town in which five civilians were killed Wednesday, a statement from Prime Minister Recep Tayyip Erdogan's office said. The town of Akcakale "was hit by artillery fire belonging to the Syrian regime forces," the statement said, in the first clear assertion of blame for the shelling. "Our armed forces on the border responded immediately to this atrocious attack within the rules of engagement, and points in Syria determined by radar were hit with artillery fire," it said. Turkey, within the confines of the rules of engagement and international law, will never leave these types of provocations aimed at our national security unanswered. Nine people were also injured when the shell landed on the town in Sanliurfa province, near the Syrian border, the statement said. The retaliatory step marks a significant increase in tension between the two countries. The Syrian government did not immediately respond to the accusation that its forces were responsible. The North Atlantic Council, NATO's most senior political governing body, was holding an urgent meeting on the situation, NATO said. Akcakale Mayor Abdulhakim Ayhan said earlier that three children, their mother and a female neighbor died when a house was hit. The artillery shell was fired from the Syrian district of Tel Abayad, according to Turkey's semiofficial Anadolu news agency. Relations between Turkey and Syria were already under strain over Damascus' response to an 18-month-long uprising against the government of President Bashar al-Assad. Before launching its military strike against Syrian targets Wednesday, Turkey reached out to NATO and U.N. chiefs. Selcuk Unal, a spokesman for the Turkish Foreign Ministry, told CNN that Foreign Minister Ahmet Davutoglu had contacted the Arab League and U.N. special envoy for Syria, Lakhdar Brahimi, about the incident. Davutoglu contacted NATO Secretary General Anders Fogh Rasmussen after the deadly shelling in Akcakale, NATO said. A senior U.S. defense official said the Pentagon is watching the situation with some degree of concern, "but at this point, there's nothing to suggest it's going to become a broader conflict." The official said the reciprocal fire appeared to be a smaller-scale border skirmish rather than a large-scale aerial bombardment. We think this is Turkey basically saying, 'Don't mess with us. Whatever is going on inside Syria, don't mess with us,'" the official told CNN. Both nations would have an interest in not allowing the conflict to escalate, according to the official. In some ways, Turkey would have more to lose in that kind of fight than Syria. They've already got a potential refugee problem coming from Syria, and a fight would only make that worse, the official said, adding that "Syria has so many problems right now, the last thing the government needs is to add another." Turkey's foreign minister called U.N. Secretary-General Ban Ki-moon to express his government's "deepest concern" about the shelling, U.N. spokesman Martin Nesirky said. Ban issued a statement expressing condolences to the shelling victims in Turkey. He called on Syria to respect the territorial integrity of its neighbors. "The secretary-general has repeatedly warned that the ongoing militarization of the conflict in Syria is leading to tragic results for the Syrian people," Ban said. Today's incidents, where firing from Syria struck a Turkish town, again demonstrated how Syria's conflict is threatening not only the security of the Syrian people but increasingly causing harm to its neighbors. Musa Ozer, who lives next to the house where the artillery shell landed, was crying as he spoke on the phone with CNN in the aftermath of the attack. He also voiced the concern felt by residents of the southeastern town. Salih Aydogdu, a local neighborhood mayor, called for authorities to act to prevent such incidents. Over the last month, we've had these types of incident five or six times. For the past two weeks, schools have been closed in the town, and the teachers have left, he added. Syria's internally displaced languish in squalor at Turkish border Rebel leadership announces move from Turkey to Syria Erdogan has repeatedly denounced Syrian President al-Assad, publicly calling on him to step down after accusing him of massacring his own people. The Turkish government continues to insist the jet was shot down by a surface-to-air missile after it left Syrian airspace -- claims that the Syrian government denies. CNN's Gul Tuysuz, Talia Kayali, Richard Roth, Chris Lawrence, Nick Paton Walsh and Saskya Vandoorne contributed to this report.