The Taliban’s rapid advance through northern Afghanistan continued on Sunday with more than a dozen districts falling to the militants, as Britain entered the final days of its two-decade deployment to Afghanistan.

More than 300 members of the Afghan security forces fled across the border into Tajikistan to escape the militants, and Badakhshan and Takhar provinces are now largely under Taliban control, beyond the respective regional capitals.

There have been no public announcements about when the last British troops will fly out. Senior sources had recently said the US and British missions would end on 4 July, but after Joe Biden backed away from that date at a weekend press conference, London appeared to follow suit.

On Friday the US handed over Bagram airbase, the heart of its campaign in Afghanistan, meaning it can no longer carry out significant operations in the country. The few hundred soldiers left are in effect on guard duty for the embassy.

But at a press conference soon afterwards, Biden brushed off questions about the end of the US deployment, saying it was a holiday weekend and “I want to talk about happy things, man”. Since then his press secretary, Jen Psaki, has reset expectations, saying the last troops would probably be out by the end of August.