The U.N. Security Council privately discussed the situation.

"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.

"The bomb fell on us. My head's really not in the right place right now," he said. "My uncle was injured and his wife died. What am I to make of this?"

Ayhan said the shell landed on one house but debris from the impact scattered across a wider area, leading to the high number of injuries.

He also voiced the concern felt by residents of the southeastern town. "The people of Akcakale are rising up against this. They live in fear," he told CNN Turk. The mayor said the shell that caused the deaths was the second to land Wednesday on Akcakale.

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. This is a small place; every time it happens, we can hear it. We are right on the border with Syria," he said. "The people of Akcakale are upset. We want the governor and the police to take precautions. This was Turkey's most peaceful and tranquil area. Now we have neither peace nor tranquility."

For the past two weeks, schools have been closed in the town, and the teachers have left, he added.

Akcakale has been rocked by previous fighting just across the border in Syria.

Last month, Turkish residents watched as Syrian shells crashed into Syrian territory, barely a stone's throw away from the Turkish border fence.

The close artillery barrage forced Turkish authorities to temporarily shut schools in Akcakale and close off roads leading to the Syrian border.

Only two years ago, Syria and Turkey enjoyed cozy bilateral relations. The neighbors had instituted visa-free travel for their citizens, and cross-border trade was booming.

Diplomatic relations ruptured, however, months after the Syrian uprising began. Last March, Turkey shuttered its embassy in Damascus and the Syrian government declared Turkey's ambassador, Omer Onhon, persona non grata.

Erdogan has repeatedly denounced Syrian President al-Assad, publicly calling on him to step down after accusing him of massacring his own people. The Syrian government, meanwhile, has accused Turkey of arming and funding Syrian rebels.

CNN journalists have witnessed light weapons in the form of assault rifles, rocket-propelled grenades and machine guns coming from Turkey to Syrian rebels.

In addition, Turkey is currently hosting more than 93,000 Syrian refugees in camps. Turkish officials estimate another 40,000 to 50,000 unofficial refugees live in Turkey outside refugee camps.

This is not the first deadly cross-border incident between the two neighbors.

On Tuesday, Turkish officials announced at least two suspected Kurdish fighters were killed after a clash broke out along the border in Turkey's Mardin province.

In June, the Syrian government announced it had shot down a Turkish military reconnaissance jet after it crossed into Syrian airspace.