The Taliban captured Afghanistan’s third-largest city and a strategic provincial capital near Kabul on Thursday, further squeezing the country’s embattled government just weeks before the end of the American military mission there.

The seizure of Herat marks the biggest prize yet for the Taliban, which has taken 11 of Afghanistan’s 34 provincial capitals as part of a weeklong blitz.

The capture of Ghazni, meanwhile, cuts off a crucial highway linking the Afghan capital with the country’s southern provinces, which similarly find themselves under assault as part of an insurgent push some 20 years after US and Nato troops invaded and ousted the Taliban government.

While Kabul itself is not directly under threat yet, the losses and the battles elsewhere further tighten the grip of a resurgent Taliban estimated to now hold some two-thirds of the nation.

Thousands of people have fled their homes amid fears the Taliban will again impose a brutal, repressive government, all but eliminating women’s rights and conducting public amputations, stonings and executions.

Peace talks in Qatar remain stalled, though diplomats met throughout the day.

The latest US military intelligence assessment suggests Kabul could come under insurgent pressure within 30 days and that, if current trends hold, the Taliban could gain full control of the country within a few months.

The Afghan government may eventually be forced to pull back to defend the capital and just a few other cities in the coming days if the Taliban keeps up its momentum.

The onslaught represents a stunning collapse of Afghan forces and renews questions about where the more than 830 billion dollars (£600 billion) spent by the US Defence Department on fighting, training those troops, and reconstruction efforts went — especially as Taliban fighters ride on American-made Humvees and pickup trucks with M-16s slung across their shoulders.

Afghan security forces and the government have not responded to repeated questions from journalists over the days of fighting, instead issuing video communiques that downplay the Taliban advance.