Activists say more than 65 civilians have died in Afrin since Turkey launched its aerial and ground campaign Jan. 20 to drive out a Syrian Kurdish militia. Ankara considers the Syrian Kurdish People's Protection Units, or YPG, an extension of the outlawed Kurdish rebels fighting an insurgency inside Turkey.
The militia has hit back with occasional rocket fire across the border.
Turkey's Anadolu Agency said Syrian Kurdish fighters in Afrin fired two rockets Wednesday, hitting a house and a garden wall in the Turkish town of Reyhanli. Two people were hospitalized after the attack and one, 17-year-old Fatma Avlar, died of her wounds, the agency said. The attacks inside Turkey have killed four people, including Avlar. Two of the victims were Syrian refugees.
The Kurdish militia, meanwhile, accused Turkey of firing Katyusha rockets into Afrin, and reported that at least 12 people were wounded in the shelling.
"We appeal to the United Nations to stop this Turkish aggression," Khalil Sabri, head of the Afrin hospital, said at a news conference aired on Kurdish and some Arab channels. "The medical supplies we have are about to run out."
The Turkish offensive has strained relations between Ankara and Washington, which has partnered with the Syrian Kurds in the fight against the Islamic State group.
U.S. troops have no presence in Afrin, but Turkey has threatened to expand the offensive to Manbij, in eastern Syria, where U.S. troops carry out regular patrols as part of the fight against the Islamic State.
On Wednesday, the top U.S. commander for the Middle East said the U.S. military is doing "everything we absolutely can" to avoid a confrontation with Turkey in Syria.
Army Gen. Joseph Votel of U.S. Central Command told reporters that there is a "robust" coordination mechanism to avoid such friction.
NATO ally Turkey views the YPG as an extension of the Kurdish insurgency it has battled for decades. The Syrian Kurdish force is a key ally of the U.S.-led coalition and has driven the Islamic State from large parts of northern and eastern Syria.