Photo taken on Aug. 22, 2021 shows foreign forces at the entering gate of Kabul airport in Kabul, Afghanistan. Seven Afghan civilians were killed amid chaos near the Kabul airport as people swarmed the area in hopes of boarding an evacuation flight following the Taliban takeover of Afghanistan, Britain's Ministry of Defense said Sunday. (Photo: Xinhua)

US troops led an increasingly desperate effort Tuesday to airlift thousands of people out of Kabul, after the Taliban warned they would allow foreign forces to carry out evacuations for just one more week.

US President Joe Biden is under increasing pressure to extend an August 31 deadline to pull out American forces, with Britain to lobby at a virtual G7 summit on Tuesday for a longer presence.

About 50,000 foreigners and Afghans have fled the country from Kabul's airport since the Taliban swept into power 10 days ago.

But crowds continued to mass outside the airport, with Afghans terrified of facing life under the Taliban.

Many fear a repeat of the interpretation of sharia law that the Taliban implemented when first in power from 1996-2001, or retribution for working with the US-backed government over the past two decades.

"The Taliban are the same as they were 20 years ago," Nilofar Bayat, a women's rights activist and former captain of Afghanistan's wheelchair basketball, said after fleeing and arriving in Spain.

"If you see Afghanistan now, it's all men, there are no women because they don't accept woman as part of society."

The Taliban, who ended two decades of war with an astonishingly swift rout of government forces, had been publicly tolerant of the evacuation effort.

But on Monday they described next week's cut-off date as a "red line."

"If the US or UK were to seek additional time to continue evacuations - the answer is no... there would be consequences," spokesperson Suhail Shaheen told Sky News on Monday.

He said any foreign military presence beyond the agreed deadline would be "extending occupation."

The Taliban achieved their stunning victory thanks to Biden's decision to accelerate a deal forged by his predecessor, US former president Donald Trump, to pull out nearly all American troops from Afghanistan.

However, he was forced to redeploy thousands of troops after the fall of Kabul to oversee the airlift.

Biden and his top aides have repeatedly insisted they are aiming to stick to their August 31 deadline.

"The goal is to get as many people out as fast as possible," Pentagon spokesperson John Kirby told reporters on Monday.

"The focus is on trying to do this as best we can, by the end of the month."

But European and British leaders are calling for more time.

British Defense Secretary Ben Wallace said Prime Minister Boris Johnson would raise the issue at the G7 virtual summit.

Germany also said it was in talks with NATO allies and the Taliban to keep Kabul's airport open for evacuations beyond August 31, while France said "additional time is needed to complete ongoing operations."

The rush to leave Kabul has sparked harrowing scenes and left at least eight people dead.

Some of them have been crushed to death and at least one, a youth soccer player, died after falling off a plane.