"Targeting innocent civilians is an act of terrorism the whole world should condemn," a Taliban official told Turkey's Habertürk TV late Thursday in the wake of the deadly twin bombings outside Afghanistan's Kabul Hamid Karzai International Airport that killed at least 90 people.

"Afghanistan won't see any more terrorist attacks after foreign forces leave," he added.

The Pentagon confirmed two separate blasts occurred near the Kabul airport, with one explosion taking place at Abbey Gate and another targeting the nearby Baron Hotel.

"We can confirm that the explosion at the Abbey Gate was the result of a complex attack that resulted in a number of U.S. and civilian casualties. We can also confirm at least one other explosion at or near the Baron Hotel, a short distance from Abbey Gate. We will continue to update," said Pentagon spokesperson John Kirby.

Another U.S. official also said the complex attack outside Kabul airport is "definitely believed" to have been carried out by the Daesh terror group.

There were, however, conflicting reports on the number of causalities.

The Pentagon said it could confirm there were casualties but did not provide a figure, adding that it expected the death toll to increase.

Another U.S. official said the blast was caused by a suicide bombing, according to Reuters.

Adam Khan, an Afghan waiting outside the airport, said the explosion went off in a crowd of people waiting to enter the airport. Khan, who said he was standing about 30 meters (100 feet) away, said several people appeared to have been killed or wounded, including some who lost body parts.

United Nations Secretary-General Antonio Guterres condemned the "terrorist attack which killed and injured a number of civilians" near the airport in Afghanistan's capital Kabul, a U.N. spokesperson said.

"This incident underscores the volatility of the situation on the ground in Afghanistan, but also strengthens our resolve as we continue to deliver urgent assistance across the country in support of the Afghan people," U.N. spokesperson Stephane Dujarric told reporters.

He said that "as far as we know at this moment" there are no casualties among U.N. staff.

NATO's chief also condemned the twin suicide bombings at the Kabul airport as a "horrific terrorist attack" that targeted desperate Afghans trying to leave the country and the alliance's efforts to evacuate them from Afghanistan.

Jens Stoltenberg said on Twitter after the explosions on Thursday: "I strongly condemn the horrific terrorist attack outside #Kabul airport. My thoughts are with all those affected and their loved ones. Our priority remains to evacuate as many people to safety as quickly as possible."

Earlier Thursday, Western nations had warned of a possible attack on Kabul’s airport in the waning days of the massive evacuation efforts. Several countries urged people to avoid the airport, where an official said there was a threat of a suicide bombing. But just days – or even hours for some nations – before the evacuation effort ends, few appeared to heed the call.

Over the last week, the airport has been the scene of some of the most searing images of the chaotic end of America's longest war ever and the Taliban's takeover, as flight after flight took off carrying those who fear a return to the militants' brutal rule.

Already, some countries have ended their evacuations and begun to withdraw their soldiers and diplomats, signaling the beginning of the end of one of history's largest airlifts. The Taliban have so far honored a pledge not to attack Western forces during the evacuation, but insist the foreign troops must be out by the U.S.' self-imposed deadline of Aug. 31.

Overnight, warnings emerged from Western capitals about a threat from the Daesh terrorist group, which likely has seen its ranks boosted by the Taliban’s freeing of prisoners during their blitz across the country.

The Taliban recently declared the war in Afghanistan over after taking control of the presidential palace in Kabul, while Western nations scrambled to evacuate their citizens amid chaos at Kabul Hamid Karzai International Airport as frantic Afghans searched for a way out.

Afghan President Ashraf Ghani said Sunday, "The Taliban have won with the judgment of their swords and guns, and are now responsible for the honor, property and self-preservation of their countrymen," after fleeing the country as the militants entered the capital virtually unopposed, saying he wanted to avoid bloodshed. The ensuing hours saw hundreds of Afghans desperate to leave Kabul airport.

"Today is a great day for the Afghan people and the mujahideen. They have witnessed the fruits of their efforts and their sacrifices for 20 years," Mohammad Naeem, the spokesperson for the Taliban's political office, told Qatar-based media outlet Al-Jazeera TV. "Thanks to God, the war is over in the country," he said.

It took the Taliban just over a week to seize control of the country after a lightning sweep that ended in Kabul as government forces, trained for two decades and equipped by the United States and others at a cost of billions of dollars, melted away.