ISTANBUL—Turkish forces shelled targets inside Syria on Wednesday afternoon after Syrian government mortar rounds hit a Turkish border town, Turkish Prime Minister Recep Tayyip Erdogan’s office said in a statement later in the day.
Turkey threatened to strike more targets inside Syria if attacks from the country are repeated, the Prime Minister’s office said, pulling a member of the North Atlantic Treaty Organization into an armed exchange with a neighbor.
NATO members convened an emergency meeting Wednesday evening. In Washington, U.S. Adm. James Stavridis, NATO’s supreme allied commander, briefed Pentagon leaders on the escalating conflict between Syria and Turkey.
Turkey’s annoucement came several hours after the government said three Syrian mortar rounds had fallen on Akcakale, a Turkish border town in the southern province of Sanliurfa, in the midafternoon. Five people were killed in the attack and 9 were wounded, the Prime Minister’s office said.
Turkey retaliated immediately, conducting mortar strikes against locations inside Syria that that had been identified by radar, the Prime Minister’s office said. Turkey adopted new rules of engagement over the summer after Syria shot down a Turkish jet.
“Our armed forces by the border have immediately responded to this reprehensible assault,” he said. “Under the rules of engagement and international law, Turkey will never let the Syrian regime’s provocations targeting our national security, such as this one, go unanswered.”
The attack and counterattack appear to open a dangerous new chapter in relations between Turkey and Syria, which were longtime allies until Syrian President Bashar al-Assad moved to crush an uprising against him that began in early 2011.
As a NATO member, Turkey is party to the founding treaty that calls, among other things, for consultations and the possibility of collective self-defense in the event of an armed attack on a NATO member.
“The latest event was the last straw,” Deputy Prime Minister Bulent Arinc said in Bursa said Wednesday. “Turkey is a sovereign country. There has been an attack against its soil and our citizens have lost their lives. There must be a response for this in international law.”
Damascus would be unlikely to purposefully target Turkish civilians and risk triggering a military conflagration with Turkey when its forces are still struggling to defeat poorly armed Sunni rebels, analysts say.
NATO members, meanwhile, have little appetite to act collectively on the issue, diplomats have said.
NATO representatives met in June, at Turkey’s request, following the downing of a Turkish jet by Syrian forces. After that meeting—called under Article 4 of the NATO treaty, under which an ally can request consultation when it believes its territorial integrity or security is threatened—the allies said they would “remain seized of developments” on the Turkish-Syrian border.
Three Syrian shells fell on Akcakale, a Turkish town in the southern province of Sanliurfa, shortly after 3:30 p.m. local time, sending residents scattering to find cover, said Abdulhakim Ayhan, the town’s mayor. Turkey’s governnment said the attack came at around 4:30.
Turkey’s government hasn’t said the strike was a deliberate attack by Syria’s military, although forces loyal to President Bashar al-Assad have been shelling rebel positions close to the border region in recent weeks.
NATO Secretary General Anders Fogh Rasmussen strongly condemned the attack during a conversation late Wednesday with Turkish Foreign Minister Ahmet Davutoglu, a NATO spokeswoman said. Mr. Rasmussen conveyed condolences and to the families of those killed and wounded and to the Turkish people.
“NATO continues to follow the situation closely and with great concern,” the spokeswoman said. She wouldn’t say whether representatives of NATO countries would meet at the alliance headquarters to discuss the incident.
The U.S. condemned the attack. “This [is a] clear violation of Turkish sovereignty,” said State Department spokeswoman Victoria Nuland. She declined to say how the attack could affect dynamics between Turkey and Syria, pending what she said would be a discussion between Secretary of State Hillary Clinton and Mr. Davutoglu later Wednesday.
In Ankara, Foreign Minister Davutoglu also called United Nations Secretary-General Ban Ki-moon and the U.N.’s Special Envoy on Syria, Lakhdar Brahimi. Turkey’s parliament cancelled its program for Thursday and will convene for a special session on Syria at 10 a.m. in Ankara.
From Akcakale, Turkish television networks showed images of smoke rising in an urban area, as policemen and soldiers herded civilians to safety. Turkey’s military began to deploy more tanks, special forces and ambulances to the region, the networks reported.
Schools closed due to heightened risks, while authorities were considering evacuating the town, said the mayor, Mr. Ayhan.
A mother and her four children were killed in the blast, according to Halil Ozcan, a lawmaker representing the region for Turkey’s governing Justice and Development Party, or AKP. A different account said the mortars had killed a mother and her three children as well as a neighbor.
The conflict in Syria has affected Turkish areas along the neighbors’ 565-mile border in the past, but Wednesday’s deaths mark a grim milestone—the first Turkish civilians to have been killed on Turkish territory as a direct result of the conflict.
For months, stray bullets have flown into Turkish territory after clashes on the Syrian side, while a mortar bomb fired from Syria damaged Turkish homes in Akcakale on Friday, although there were no casualties.
Syria’s June downing of the Turkish jet left the two pilots dead, pushing Ankara to reinforce its side of the border with heavy armor and change its rules of engagement to reflect the rising possibility of further infringements.
Analysts said that although Turkey had responded to the cross-border incidents cautiously thus far, the deaths of a civilian family would add a great deal of pressure to take firmer action.
“This may be one step too far for Turkey to absorb. The government has been criticized for not acting more forcefully,” said Sinan Ulgen, a former Turkish diplomat now with the Carnegie Endowment in Brussels.
“Now, I can’t tell you with a degree of confidence that the response this time will be diplomatic. A surgical strike using Turkey’s special forces against identified targets that are at the root of this aggression could well happen.”
Turkish television showed images of residents in Akcakale protesting after the shells struck, although it wasn’t clear if they were demanding retaliation.
The Turkish government, which is spearheading efforts to force Syrian President Assad from power, has faced growing public skepticism over its Syria policy, as the civil war next door has spilled increasingly across the border.
More than 82,000 Syrians have sought refuge in Turkey, at a cost of around $300 million to the Turkish government, Ankara said Tuesday, as Turkish border towns that relied on trade with Syria have seen economic activity wither and unemployment rise.
Turkish television has shown footage of Turks who were kidnapped in Syria and Lebanon by groups loyal to Damascus, which were targeting Turks seemingly due to Ankara’s anti-Assad stance.
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