Clashes between US-backed Syrian Kurdish fighters and members of the ISIS group killed at least three people inside a restive camp in northeastern Syria that houses ISIS families, a Kurdish official and an opposition war monitor said Tuesday. The clashes broke out late Monday night at al-Hol in Syria’s province of Hasakah, when Kurdish fighters exchanged fire with an ISIS sleeper cell, according to Shixmus Ehmed, head of the Kurdish-led administration’s department for refugees and displaced. He spoke to The Associated Press via voice messages Tuesday. The fighting involving automatic rifles and rocket propelled grenades, he said, adding that the situation remains tense. The sprawling al-Hol camp has for years held tens of thousands of women and children — mostly wives, widows and children of ISIS members. Syrian Kurdish fighters have intensified their inspections at al-Hol in recent weeks following a late January attack by ISIS on a prison in the provincial capital of Hasakah, where some 3,000 militants and juveniles are held. That attack led to 10 days of fighting between the US-backed fighters and ISIS militants that left nearly 500 people dead before the situation was brought under control. It was the biggest attack by ISIS since the fall of the group’s so-called Islamic “caliphate” in 2019, and stoked fears it may be staging a comeback. Following the Sunday night clashes, the Kurdish fighters surrounded the area to prevent any ISIS gunmen from escaping, Ehmed said, without giving a breakdown for the casualties. The Britain-based Syrian Observatory for Human rights, an opposition war monitor, said a woman and a child were killed as well as an ISIS militant. The Observatory added that four women and six children were wounded. The Kurdish fighters imposed a curfew inside the camp, the Observatory also said, adding that the fighting was concentrated in areas housing family members of Iraqi and Syrian ISIS militants. Some 50,000 Syrians and Iraqis are located in al-Hol. Nearly 20,000 of them are children while the rest are mostly women. A nearby separate and heavily guarded section of the camp known as the “annex" is where about 2,000 women from 57 other countries are held, with about 8,000 children. The women in the annex are considered to be the most die-hard ISIS supporters. In February, women at al-Hol tried to kidnap their Kurdish guards, leading to a shooting that left one child dead and several people wounded. ISIS leader Abu Ibrahim al-Hashimi al-Qurayshi was killed days after the January prison attack. US officials said he blew himself up along with members of his family as American forces raided his hideout in the northwestern Syrian town of Atmeh, near the border with Turkey, on Feb. 3. The ISIS group has named Abu al-Hassan al-Hashimi al-Qurayshi as its new leader.