Through setting an unconditional and complete withdrawal from Afghanistan by September 11, U.S. President Joe Biden has "triggered an unseemly military scramble for the exit that has been joined by all residual Nato forces, including most UK troops ... without ceremony or fanfare, almost by the back door," UK newspaper The Observer warned in an editorial on Sunday.

"The fourth of July is American independence day. It may also come to be remembered as deserting Afghanistan day," the sister paper of The Guardian added. "Like Iraq, coldly abandoned to its fate 10 years ago, Afghanistan's post-American future is deeply daunting."

Several districts of northern Afghanistan were taken overnight by the Taliban as U.S. forces continued to withdraw from the region, officials said Sunday. Since mid-April, when Biden announced the end to the "forever war" in Afghanistan, the Taliban has made strides throughout the country. Its most significant gains have been in the northern half of the country, a traditional stronghold of the U.S.-allied warlords who helped defeat them in 2001.

The Taliban now controls roughly a third of the 421 districts and district centers in Afghanistan, according to the Associated Press.

Security experts also expressed concern about the complicated situation the United Kingdom may face in the future due to the withdrawal. 

"The threat to the UK from terrorist groups like al Qaeda will grow if allies turn their back on Afghanistan after troops withdraw," warned Sir Alex Younger, the former chief of MI6 (the UK's foreign intelligence service), according to a Sky News report on Monday.