At least 17 people were killed when an Islamic State-affiliated rebel group attacked a hospital in eastern Congo, officials said Saturday.

The Allied Democratic Forces (ADF) struck on Friday night in Byambwe village, Lubero territory, North Kivu province, Col. Alain Kiwewa, the local administrator, told The Associated Press. He said 11 women, including breastfeeding mothers, were found dead with their throats slit in hospital beds.

ADF fighters also assaulted nearby villages, according to civil society leader Samuel Kakule Kagheni, though casualty figures there remain unclear.

The ADF, which pledged allegiance to the Islamic State in 2009, is active along the Uganda-Congo border and frequently targets civilians. Other armed groups, including the Rwanda-backed M23 rebels, have also carried out deadly attacks in eastern Congo.

In recent months, the ADF has carried out multiple lethal assaults, including killing 52 people in August and nearly 40 worshippers during a church attack in Ituri province in July.

Originally formed in Uganda in the late 1990s amid opposition to President Yoweri Museveni, the ADF relocated to Congo in 2002 following Ugandan military action. Since then, it has been responsible for the deaths of thousands of civilians.