Afghanistan troop pullout a 'mistake': George W. Bush

Former US president George W. Bush on Wednesday criticised the withdrawal of NATO troops from Afghanistan and said civilians were being left to be "slaughtered" by the Taliban.

"Afghan women and girls are going to suffer unspeakable harm. This is a mistake... They're just going to be left behind to be slaughtered by these very brutal people, and it breaks my heart," Bush told German broadcaster Deutsche Welle.

The former Republican president, who sent troops to Afghanistan in autumn 2001 after the September 11 attacks on New York's World Trade Center, said he believed German Chancellor Angela Merkel "feels the same way".

Bush said Merkel, who is set to retire from politics later this year after 16 years in power, had brought "class and dignity to a very important position and made very hard decisions".

US and NATO forces began withdrawing from Afghanistan in early May and are due to completely pull out by September 11, some 20 years after they arrived in the war-torn country.

Most of the 2,500 US and 7,500 NATO troops who were in Afghanistan when US President Joe Biden detailed the final withdrawal in April have now gone, leaving Afghan troops to fight an emboldened Taliban seemingly bent on a military victory.

The country is facing a crisis as the insurgents snap up territory across the countryside, stretching government forces and leading to a fresh wave of internally displaced families, complicated by a renewed outbreak of Covid-19.

The United Nations said on Sunday the rising conflict is causing "more suffering" across the violence-wracked country as it called for continuous financial aid.

Biden has insisted, however, that it is time for US involvement in the war to end and for Afghans to chart their own future.