"I appeal to the Security Council – and the international community as a whole – to stand together, work together and act together – and use all tools at its disposal to suppress the global terrorist threat in Afghanistan and guarantee that basic human rights will be respected," Guterres told the Security Council.
"Regardless of who holds power, these two fundamental principles — in which our world has such a deep and abiding interest — must be upheld," he added.
The stark warning comes after the Taliban laid claim to the capital Kabul, where thousands of people who fled the group's offensive elsewhere in the country had sought refuge.
Ghulam Isaczai, Afghanistan's envoy to the UN, warned that Kabul's residents "are living in absolute fear right now,” imploring the Security Council and Guterres to do everything in their power to ensure Afghanistan does not descend "into a civil war," and become again "a pariah state."
"Kabul residents are reporting the Taliban have already started house-to-house searches in some neighborhoods, registering names and looking for people on their target list," he said. "There are already reports of targeted killings and looting in the city."
The Taliban have rapidly claimed a majority of the country in a lightning offensive that has blindsided western powers as Afghan forces melted away. Kabul fell to the group on Sunday after the Afghan government collapsed and former President Ashraf Ghani fled the country.
Following the departure of Ghani, former President Hamid Karzai, veteran politician Gulbuddin Hekmatyar and top peace negotiator Abdullah Abdullah have been working to ensure a smooth transfer of power.
The US is in the midst of evacuating its diplomatic personnel from Kabul's Hamid Karzai International Airport, as well as thousands of Afghan refugees who are seeking refugee status.
Washington called on all Afghan parties "to ensure safe departures, and the protection of human life and property" as it carries out the operation.
"I want to reiterate, reemphasize and reassert this call. Civilian populations, including journalists and non-combatants must be protected," Ambassador Linda Thomas-Greenfield said.
"Attacks against civilians or civilian objects must stop, and the human rights and fundamental freedoms of all Afghan citizens, especially women, girls and members of minority groups must be respected," she added.
Russia's UN envoy, Vasily Nebenzya, meanwhile said there is "no point in panicking," maintaining the worst-case scenario has been avoided.
"The main point is that a widespread bloodbath among civilians has been avoided," he said. "We urge all Afghan parties to refrain from hostilities and to foster a settlement peacefully. We believe that the international community must help Afghanistan, they must pool their efforts to help Afghanistan achieve national reconciliation.”
Russia's embassy in Kabul has remained open, and the Kremlin has acknowledged it established "working contacts" with the Taliban.
