Two suicide bombers and gunmen attacked crowds of Afghans flocking to Kabul's airport Thursday, transforming a scene of desperation into one of horror in the waning days of an airlift for those fleeing the Taliban takeover. At least 60 Afghans and 12 U.S. troops were killed, Afghan and U.S. officials said. 

U.S. officials said 11 Marines and one Navy medic were among those who died. They said another 12 service members were wounded and warned the toll could grow. More than 140 Afghans were wounded, an Afghan official said. 

One of the bombers struck people standing knee-deep in a wastewater canal under the sweltering sun, throwing bodies into the fetid water. Those who moments earlier had hoped to get on flights out could be seen carrying the wounded to ambulances in a daze, their own clothes darkened with blood. 

A U.S. official said the complex attack was believed to have been carried out by the Islamic State group. The IS affiliate in Afghanistan is far more radical than the Taliban, who recently took control of the country in a lightning blitz and condemned the attack. 

Western officials had warned of a major attack, urging people to leave the airport, but that advice went largely unheeded by Afghans desperate to escape the country in the last few days of an American-led evacuation before the U.S. officially ends its 20-year presence on Aug. 31. 

Emergency, an Italian charity that operates hospitals in Afghanistan, said it had received at least 60 patients wounded in the airport attack, in addition to 10 who were dead when they arrived. 

"Surgeons will be working into the night," said Marco Puntin, the charity's manager in Afghanistan. The wounded overflowed the triage zone into the physiotherapy area and more beds were being added, he said. 

US President Joe Biden has cancelled all his appointments while monitoring the unfolding events. 

He called the situation "close-up war". 

"We are saddened by the loss of lives, both US and Afghan, but we will continue to execute our mission." 

Emergency, an Italian charity that operates hospitals in Afghanistan, said it had received 60 patients wounded in the airport attack, in addition to 10 who were dead when they arrived. 

"Surgeons will be working into the night," said Marco Puntin, the charity's manager in Afghanistan. The wounded overflowed the triage zone into the physiotherapy area and more beds were being added, he said. 

One of the bombers struck people standing knee-deep in a wastewater canal under the sweltering sun, throwing bodies into the fetid water. Those who moments earlier had hoped to get on flights out could be seen carrying the wounded to ambulances in a daze, their own clothes darkened with blood. 

A US official said the complex attack was believed to have been carried out by the Islamic State group. The IS affiliate in Afghanistan is far more radical than the Taliban, who recently took control of the country in a lightning blitz and condemned the attack. 

Western officials had warned of a major attack, urging people to leave the airport, but that advice went largely unheeded by Afghans desperate to escape the country in the last few days of an American-led evacuation before the US officially ends its 20-year presence on August 31. 

Those registered on the New Zealand Government's Safe Travel website were also warned to stay away, the airport having been judged as simply too dangerous. 

At least 13 people died and 15 were wounded, according to Russia's Foreign Ministry, which gave the first official casualty count. Pentagon spokesman John Kirby also confirmed the blasts and said there were casualties, including among members of the military, but gave no figure. He said one explosion was near an airport entrance and another was a short distance away by a hotel. 

One official, who spoke on condition of anonymity to discuss ongoing military operations, said several Marines were killed. American officials have said that information is still coming in and they are trying to determine exact numbers of casualties. 

Two suicide bombers and gunmen have targeted crowds massing near the Kabul airport. Photo / Wali Sabawoon, AP 

Even as the area was hit, evacuation flights continued to take off from Kabul airport. 

Taliban spokesman Zabihullah Mujahid had earlier denied that any attack was imminent at the airport, where the group's fighters have deployed and occasionally used heavy-handed tactics to control the crowds. 

Prior to the blasts, the Taliban sprayed a water cannon at those gathered at one airport gate to try to drive the crowd away, as someone launched tear gas canisters elsewhere. 

After the attack, Mujahid pointed out the airport is controlled by US troops. 

Adam Khan was waiting nearby when he saw the first explosion outside what's known as the Abbey gate. He said several people appeared to have been killed or wounded, including some who were maimed. 

The second blast was at or near Baron Hotel, where many people, including Afghans, Britons and Americans, were told to gather in recent days before heading to the airport for evacuation. 

A former Royal Marine who runs an animal shelter in Afghanistan says he and his staff were caught up in the aftermath of the blast near the airport. 

"All of a sudden we heard gunshots and our vehicle was targeted, had our driver not turned around he would have been shot in the head by a man with an AK-47," Paul "Pen" Farthing told Britain's Press Association news agency. 

The White House hurriedly put off President Biden's first in-person meeting with Israel's new prime minister Thursday and canceled a video conference with governors on incoming Afghan refugees after the explosions outside the Kabul airport. 

Biden was to host Naftali Bennett, Israel's new Prime Minister, who is on his first visit to the US since taking office. Biden also had planned to meet virtually with a bipartisan group of governors who have said they want to help resettle Afghan refugees fleeing their now Taliban-ruled country. 

But the deadly developments in the Afghan capital of Kabul forced the White House to tear up the president's schedule, as he monitored the airport situation that was prompted by the Tuesday deadline he set for removing American citizens and troops from Afghanistan. 

Despite intense pressure to extend the Tuesday deadline, Biden has repeatedly cited the threat of terrorist attacks against civilians and US service members as a reason to keep to his plan. 

The explosions detonated as the US worked to get remaining Americans out of the country. 

Secretary of State Antony Blinken said Wednesday that as many as 1500 Americans may be awaiting evacuation. 

Asked during an interview with ABC News about reports the evacuation could end on Friday, Ross Wilson, the US ambassador to Afghanistan, declined to comment. Wilson said "there are safe ways to get to" the airport for those Americans who still want to leave. He added that "there undoubtedly will be" some at-risk Afghans who will not get out before Biden's deadline.

- Sayed Ziamal Hashemi, Lolita C. Baldor & Joseph Krauss of AP