American citizens trying to get in to Kabul airport and leave the country were told on Wednesday night to immediately leave the area, due to a new and sudden terror threat.

'Due to threats outside the Kabul airport, US citizens should avoid traveling to the airport and avoid airport gates unless you receive instructions to do so,' the State Department tweeted on Wednesday night. 

'Those at the Abbey Gate, East Gate, or North Gate now should leave immediately.' 

The order to leave the gates was issued at 3:30am local time in Kabul on Thursday morning. 

Fears are mounting that the Islamic State affiliate in the region, ISIS-K, could try and launch an attack on the crowds masses outside the airport. Joe Biden on Tuesday warned that ISIS-K were believed to be attempting to target departing jets, as he explained why it was unlikely that U.S. forces will remain in the area beyond August 31.

Up to 1,500 Americans are still trapped in Afghanistan and the U.S. is still relying on the Taliban to allow safe passage to Kabul airport with just six days before the deadline, Secretary of State Anthony Blinken said in a press conference on Wednesday.

Blinken gave his first briefing on the airlift operation and the bid to get all citizens and Afghan allies out amid reports the CIA has joined U.S. troops in helicopter rescue missions outside the airport perimeter.