The German Embassy issued a similar warning, saying Taliban forces were conducting increasingly strict controls in the area.

The security threats have prompted the U.S. military to come up with ways to get evacuees to the airport, a U.S. official said Saturday, according to The Associated Press.

One possible solution would involve small groups gathering at specific points where the U.S. military would pick them up, the source said.

U.S. officials who spoke anonymously declined to provide details about the IS threats but said they were significant, although no attacks had been confirmed.

The U.S. also was continuing to communicate with local Taliban commanders to move people through their checkpoints.

The U.S. military evacuated about 3,800 people from Hamid Karzai International Airport in Kabul in the past 24 hours, the White House announced Saturday, and 17,000 since August 14, the Saturday before the Taliban entered Kabul.

The White House said about 22,000 people had been evacuated since the end of July.

Among the 17,000 evacuated over the past week were 2,500 Americans, Army Major General William Taylor said Saturday at a Pentagon media briefing.

Pentagon spokesman John Kirby told reporters at the briefing he did not have a “perfect figure” indicating how many Americans remained in Kabul and in other parts of Afghanistan.

U.S. President Joe Biden reiterated a vow Friday to stay in Afghanistan until all American citizens who wanted to leave and Afghans who risked their lives working for the U.S. government during the conflict had been evacuated.

"Any American who wants to come home, we will get you home. Make no mistake, this is dangerous. It involves risks to our armed forces and is being conducted under difficult circumstances," Biden said alongside Vice President Kamala Harris and Secretary of State Antony Blinken at the White House.

Biden also said his administration would do "everything that we can" to safely evacuate "our Afghan allies, partners and Afghans who might be targeted."

Taylor told reporters Friday that there were about 5,800 U.S. troops at the airport in Kabul to help the evacuation efforts.

He said evacuations stopped Friday for more than six hours because of a backup at a refugee transit point at a U.S. airbase in Qatar. Taylor said that the flights resumed later in the day and that, in general, evacuation flights were steadily increasing.

On Saturday, the White House said evacuees had been taken out on six flights using C-17 aircraft and 32 flights on chartered planes.

Despite the chaos and occasional violence outside the airport, the president has stressed that the U.S. military is in control at the airport and is evacuating thousands, with the goal of getting everyone who needs to be evacuated, both American and Afghan, out by August 31.

VOA's Patsy Widakuswara and Steve Herman contributed to this report. 

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