British Prime Minister Boris Johnson has said that he would work with the Taliban if necessary to “find a solution” for Afghanistan, as the UK government navigates “formidable” challenges in evacuating people from Kabul.

The British prime minister also sought to defend Dominic Raab, the under-fire foreign secretary who has faced a litany of questions over his handling of the crisis, insisting he “absolutely” had confidence in the cabinet minister.

"What I want to assure people is that our political and diplomatic efforts to find a solution for Afghanistan, working with the Taliban, of course if necessary, will go on," Johnson told media.

Johnson said the situation at Kabul airport, where thousands of desperate Afghans have thronged seeking exodus from the country, was getting "slightly better".

The British government said it had secured the evacuation of 1,615 people since Saturday, including 399 British nationals and their dependants, 320 embassy staff and 402 Afghans.

Asked if he still had confidence in Foreign Secretary Dominic Raab who has faced calls for his resignation from opponents for his response to the crisis, he said: "Absolutely".