AKCAKALE, Turkey — Shells and rockets landed in several Turkish border towns on Thursday, killing four civilians, one of them an infant, and wounding 70, in a sharp escalation of the conflict between the Turkish state and the Kurdish militias who fought alongside American forces in the campaign to contain Islamist extremists in northern Syria.
The attack came as a Turkish offensive against Kurdish fighters in northern Syria entered its second day, with Turkish troops continuing an air and ground assault against the Kurdish groups, killing at least 16 Kurds, rights groups reported.
By Thursday morning, Turkey had conducted 181 airstrikes in the area, its Defense Ministry said. The Turks also used cranes to remove parts of a concrete border wall, allowing Turkish troops and military vehicles to enter Kurdish-held territory in northern Syria.
Turkish-backed Syrian Arab rebel fighters said they had taken at least one formerly Kurdish-held village that lies just meters from the border.
On Thursday afternoon, Kurdish fighters appeared to return fire, as three sharp explosions in Akcakale filled streets around the town’s police headquarters with smoke, and sent pedestrians fleeing for cover and armored police vehicles barreling through the streets.
On both sides of the border, droves of civilians crammed into cars and pickup trucks to search for safety from the fighting.
More than 60,000 Syrians in Kurdish-held territory have fled away from the border since Wednesday, according to the Syrian Observatory for Human Rights, a conflict monitor based in Britain, and United Nations officials.
The fighting, which began Wednesday, marks a new stage in the eight-year-old Syrian civil war that began as a wave of protests against President Bashar Assad of Syria, but which has since escalated into a jumble of overlapping conflicts involving foreign armies and an array of local militias including former Syrian government officers, Islamist extremists and Kurdish nationalists.
The United States joined forces with a Kurdish-led militia, the Syrian Democratic Forces, to clear northeastern Syria of militants from the Islamic State. Kurdish groups seized the opportunity to carve out an autonomous statelet in northeastern Syria, buttressing the southern Turkish border.
The Kurdish presence, abutting the Turkish border, enraged the Turkish government, which considers the Kurdish-led militia an enemy because of its ties to a Kurdish guerrilla force inside Turkey.
For several years, a small US force kept the peace between the Syrian Kurds and Turkey — until President Trump’s sudden decision on Sunday to pull US troops out of Turkey’s way, despite qualms from his own military officers and State Department officials, and criticism from Republican politicians.
On Thursday afternoon, President Recep Tayyip Erdogan of Turkey characterized the invasion as an attempt to preserve Syria’s long-term sovereignty and to clear the area of not just Kurdish fighters but also the remnants of the Islamic State.
“The aim of Operation Peace Spring is to contribute to the territorial integrity and political union of Syria,” Erdogan said in a speech to his political party, using the Turkish military’s name for the invasion.
Erdogan dismissed concerns that the mayhem of the invasion would risk allowing thousands of Islamic State militants detained by the Kurdish-led militia to escape.
“We will keep in jail the ones who should be kept in jail and send the other ones to their countries of origin, if those countries accept them,” he said.
President Emmanuel Macron of France condemned the offensive on Thursday, calling for Turkey to end it “as quickly as possible.”
“Today Turkey is forgetting that the international community’s priority in Syria is the fight against Daesh and terrorism,” he said, using another name for the Islamic State, and adding that Turkey was risking a humanitarian crisis for “millions of people.”
“This risk of helping Daesh rebuild a caliphate, and this humanitarian risk, is Turkey’s sole responsibility before the international community,” he said.
Turkish officials said that 109 Kurdish fighters had been killed since Wednesday, though independent monitors reported lower estimates. At least 16 Kurds were reported to have been killed, one monitoring group said.
Members of the Syrian Democratic Forces were killed in the area of Tel Abyad and Ras al-Ain in northeastern Syria, along with six attackers of unknown identity, according to the Syrian Observatory for Human Rights. US troops had withdrawn from both areas Monday.
An additional 33 members of the Syrian Democratic Forces were wounded, the monitoring group said.
Days after greenlighting the Turkish operation, Trump condemned it as a “bad idea” on Wednesday. He said this week that Turkey, a NATO ally, would face economic punishment if it did anything he considered “off limits.”
In a statement on Wednesday, Turkey’s defense minister, Hulusi Akar, said the aims of the operation were to “ensure the security of our borders and the safety of our people,” naming Kurdish militias and Islamic State militants as threats.
Six hours of airstrikes ensued, followed by Turkish and rebel Syrian Arab ground troops crossing the border into Syria.
Reached by telephone inside Syria, a member of a Syrian Arab militia said around a brigade of around 1,000 Turkish-backed Syrian fighters had taken the town of al-Yabseh, after meeting no resistance.
“We captured the town an hour ago without any clashes,” said al-Hareth Dahdouni, 31, a representative of the Shami Front, a Turkish-backed Syrian militia. “The town was totally empty. It is just one minute away from the border.”
The fighting threatens to create a humanitarian crisis for hundreds of thousands of people who have been cut off from Syrian assistance for years. Most rely on the Kurdish forces and aid groups for basic services. Civilians jammed roads while fleeing with their possessions on Wednesday.
The impact of the assault was “a lot worse, a lot more dramatic” than aid organizations had feared, Panos Moumtzis, the United Nations humanitarian aid coordinator in Syria, said in a telephone interview. “The protection of civilians is now the biggest concern.”
Some aid organizations had already evacuated personnel from the area, he added.
Hundreds of thousands of civilians “are now in harms way,” Filippo Grandi, head of the UN refugee agency, said in a statement.
Henrietta Fore, the executive director of UNICEF, said in a statement on Wednesday that the military escalation would have “dramatic consequences” on the ability to provide aid.
“I urge all parties to protect children and the civilian infrastructure on which they depend, in accordance with international human rights and humanitarian law,” she said. “The use of explosive weapons in populated areas causes unacceptable harm to children.”
Inside Turkey, families also began loading up their belongings and leaving town to travel away from the border. “We are going west because people were hit on the east side of town,” said Ayse Kaya as she piled her family into a small car.
But others, including Syrian refugees now living in Turkey, were less concerned.
“I have seen this before, I am from Syria, I am going to prepare a shisha,” said Mustafa Ali, an elderly man in a long cotton robe, referring to a traditional waterpipe. “I came from Aleppo, I saw many of these in Aleppo. I am going to prepare a pipe at home.”
Ali also expressed support for the Turkish operation, which he hoped would allow Syrian Arabs to regain control of Kurdish-held territory. “What we need is for Turkey to clean our land and then we can go back to our land,” he said.