Turkey continued to fire artillery at a US-backed Kurdish militia in northern Syria on Sunday, after Turkey's state media said four rockets from Syria had hit a Turkish border town.
The cross-border fire marked the second day of Turkey's new front in the nearly seven-year-old Syrian civil war. Under "Operation Olive Branch", Turkish airstrikes on Saturday pounded positions of the Syrian-Kurdish YPG militia in the northern Afrin province.
A Reuters reporter at the Oncupinar gate on the Turkish side of the border with Syria, could hear the boom of outgoing artillery, with one being fired roughly every three minutes.
Military convoys were travelling near the gate, with one transporter carrying several tanks.
"In its second day, #OliveBranchOperation continues to ensure peace and security for our people, protect Syria’s territorial integrity and eliminate all terrorist elements in the region," Turkish President Tayyip Erdogan's spokesman, Ibrahim Kalin, said on Twitter.
"Turkey expects its allies to support its fight against terrorism in all of its forms."
Turkey's state-run Anadolu news agency earlier reported that four rockets fired from Syria hit the border town of Kilis overnight, damaging houses.
Turkish security forces retaliated in kind, it said.
The operation pits Turkey against Kurdish fighters allied to the United States at a time when ties between Turkey and Washington - NATO allies and members of the coalition against Islamic State - appear dangerously close to a breaking point.
Saturday's strikes on the Syrian-Kurdish YPG militia hit some 108 targets, the Turkish military said. On land, the Turkey-backed Free Syrian Army rebels were also helping the operation in Afrin, Turkish officials have said.
Turkey sees the YPG as an extension of the outlawed Kurdistan Workers Party (PKK), which has carried out a deadly, three-decade insurgency in Turkey's mainly Kurdish southeast.
The United States is backing the YPG in Syria, seeing it as an effective partner in the fight against Islamic State.