Turkish officials said the troops entered the enclave a day after dozens of Turkish jets and Turkish artillery units at the border pounded Syrian Kurdish targets as part of an offensive, codenamed Olive Branch.

Turkish President Recep Tayyip Erdogan has promised to expand the operation to other Kurdish regions. Turkish media reports have quoted Prime Minister Binali Yildirim as telling a group of journalists on Sunday that Turkey aims to create a 30-kilometer deep "secure zone" in Afrin.

Earlier Sunday, four rockets fired from Syria hit the Turkish border town of Kilis, prompting Turkish artillery to return fire, Gov. Mehmet Tekinarslan said. The rockets hit two offices and an office building, and slightly wounded one person.

The state-run Anadolu Agency said the Turkish-backed fighters had penetrated 5 kilometers into Afrin.

Turkey has prepared around 10,000 Syrian fighters to storm Afrin, according Rami Abdurrahman, director of the Syrian Observatory for Human Rights, a Britain-based monitoring group.

Reporter’s code: 50101