SANAA, Yemen (AP) — Yemeni military forces fought to retake areas held by Islamist militants in fierce clashes Saturday in the southern port city of Aden, security officials said.

The clashes in Aden's Mansoura district have expanded southward as civilians in the area fled their homes, while five civilians were injured from shrapnel and gunfire were taken to a local hospital, medical officials said.

Local affiliates of both al-Qaida and the Islamist State are fighting against security forces, with the fighters using heavy weapons in guerrilla warfare. A Saudi-led coalition started bombing Islamist locations in the city for the first time, the officials said.

Al-Qaida and the Islamic State have exploited the chaos of Yemen's 18-month civil war to expand the territory under their control in southern and eastern Yemen.

Yemen has been torn by conflict since 2014, when Shiite rebels known as Houthis and allied with a former president captured large swaths of the country, including the capital, Sanaa.