KABUL — The beheadings of women and a child by ISIS-linked militants in Afghanistan and a propaganda video showing extremists overrunning an army base have raised fears that the group's supporters are tightening their grip on parts of the country.
The seven civilians beheaded were Hazaras, an ethnic and religious minority that have been discriminated against for centuries in Afghanistan. Fellow Shiite Muslims have also been massacred by ISIS and other extremist groups in neighboring Pakistan, as well as in Iraq and Syria.
Thousands of mainly Hazaras carried the bodies of the victims through the streets of Kabul on Wednesday and called on the government to halt sectarian violence. Hazaras were oppressed and massacred by the Taliban government before it was toppled by U.S.-backed forces in 2001.
GALLERY: Afghans Fill Streets to Protest Beheadings
"We are all here — Hazara, Pashtun, Tajik, Uzbek — to demand justice," protester Kamela, a 22-year-old university student, told NBC News referring to the country's main ethnic groups. "We will not go back to those days," she added, referring to the Taliban era, and the country's civil war which saw ethnic militias turning on each other.
ISIS-linked Uzbek militants who provincial officials believe kidnapped and killed the Hazaras in the southern province of Zabul over the weekend are fighting alongside a fighters struggling to wrest control of the Taliban away from Mullah Akhtar Mohammad Mansour, who took over in July.
Around 400 Uzbeks are fighting with the faction led by Mullah Mohammad Rasool Akhund, according to a spokesman for the group, Abdul Manan Niazi. The Islamic Movement of Uzbekistan (IMU) pledged their loyalty to ISIS in a video released on July 31.
Related: Who's Who Under New Militant Chief Mansour
Militants linked to ISIS have made some inroads in the regions, luring members of the Taliban who are unhappy with the Afghan group's leadership.
"These are foreign militants who in collaboration with some Afghan militants have changed their flag to black and carry out atrocities on our people," Interior Ministry spokesperson Najib Danish told NBC News. He was referring to the change of allegiance from the white Taliban flag to the black ISIS banner.
Uzbek fighters have the reputation of being particularly brutal, according to Taliban commanders who have fought with them.
They "introduced the culture of beheading" into the Taliban, one Taliban commander told NBC News on condition of anonymity. "They were known for their barbarism and ruthlessness."
The IMU militants are thought to have kidnapped the civilians before heavy fighting against Taliban fighters loyal to Mansour, Deputy Governor Massoud Bakhtawar told NBC News. It was not known exactly when they were killed.
The slayings underlined the impression that ISIS is on the move across the country — an impression fed by the release of a new ISIS propaganda video.
It includes the first footage showing the group carrying out a coordinated attack on a military outpost in Afghanistan, according to Laith Alkhouri, director of research and analysis for Middle East and North Africa at global security firm Flashpoint Intelligence.
The 17-minute video released on Monday comes after the group declared in January that neighbors Pakistan and Afghanistan should be one region called the province of Khorasan.
Alkhouri called the footage "unprecedented," and showed "an ISIS-style attack," similar to those carried out in Iraq and Syria. "They are essentially copying from ISIS military manual," Alkhouri added.
At the start of the video, the word "Khurasan" — a historic region that covers part of modern-day Iran, Afghanistan and Pakistan — appears against a black screen in both Arabic and English.
Fighters are soon seen and heard discussing the assault, praying and then setting off towards the base, which sits at the top of a hill. Later, bodies of slain Afghan soldiers are shown in gruesome detail and ISIS fighters are seen giving prayers of thanks for their victory.
The base in Achin District in Nangahar province some 90 miles east of Kabul was retaken by Afghan Army soldiers later in July, according to district chief Haji Ghalib.
Despite the advances, Alkhouri said ISIS was a long way from overrunning the country, as it has done in huge parts of Syria and Iraq.
"When we put it in a comparative analysis [ISIS] are still a small part of the insurgency," he said.
