The UK needs to face the “new reality” in Afghanistan and work with other nations to exercise a “moderating influence” on the Taliban, the foreign secretary has said.

Dominic Raab said the UK would hold the Taliban to its pledge of safe passage for those who want to leave.

The number of UK nationals still there was in the “low hundreds”, he added.

He said over 5,000 UK nationals were among more than 17,000 people evacuated by the UK from Afghanistan.

Mr Raab also defended his handling of the crisis, insisting that “no department has performed better than the Foreign Office and anyone trying to suggest otherwise” either lacked “credibility” or had been “peripheral” to events – and “should be focused on the job at hand”.

The foreign secretary told BBC Breakfast that the next “challenge” was to face Afghanistan’s “new reality…and come up with a plan that reflects it”.

He said the UK needed to get “wider buy in” from China, Russia and countries in Central Asia to exercise the “maximum moderating influence” on the Taliban and safeguard gains made over two decades, such as better access to education and lower maternal mortality rates.

Mr Raab said he did not recognise claims that the UK asked for a gate at Kabul airport to be left open to assist its evacuations hours before Thursday’s suicide bombing – despite US military leaders wanting to close it to minimise the risk.

“We did everything we could once we were alerted to the threat before the explosion took place to mitigate the risk,” Mr Raab said – including warning people to stay away, asking crowds to leave, and moving the UK’s civilian team from the Baron Hotel to the airport.

“None of that would have required or necessitated the gate at Abbey Gate to be left open.”

He added that the UK would “reserve the right” to take part in future air strikes in the country on the grounds of “lawful self-defence”, especially when dealing with “terrorist groups”.

His comments came after the head of the RAF, Air Chief Marshal Sir Mike Wigston, told the Daily Telegraph that British forces would be prepared to launch air strikes, adding: “We’ve got to be able to play a global role in the global coalition to defeat Daesh, whether it’s strike, or whether it’s moving troops or equipment into a particular country, at scale and at speed.”

The Taliban have declared victory in Afghanistan following the withdrawal of US troops, with fighters streaming into Kabul airport on Tuesday. British troops left the country over the weekend.

In a draft resolution adopted on Monday evening, the United Nations Security Council urged the Taliban to let people leave the country, and not to allow it to become a base for terrorism.

And it called on all parties to allow “full, safe and unhindered access” for the UN and charities to deliver humanitarian aid.

The resolution, drafted by the UK and France, was passed with 13 votes in favour and two abstentions, from China and Russia.

A former English language teacher who is stranded in Kabul told BBC Radio 4’s Today programme he regretted working with the UK mission because he now fears for his life.

“I regret working with the English. I regret helping people learn English. Why did I work for people who left me and fled and left me alone here?” he asked.

The teacher, who the BBC is not naming, said he worked for the UK for eight or nine years, including for the British Council, and was now a target for the Taliban.

“They are looking for me because I’ve got pictures in billboards advertised for classes,” he said.

He said he tried to escape Afghanistan shortly before the militants took control but received “no reply” to his application for resettlement, adding that he had been unable to sleep ever since.

“The whole night, guns while you’re sleeping. It damages your mind,” he said.

Asked what he thought would happen to him if he could not leave and the Taliban found him, he added: “My fate will be the same, like others, like the people who work in military in the media… they will kill me too.”

The Taliban have promised those with authorisation will be allowed to leave the country, and US Secretary of State Anthony Blinken pledged to “hold the Taliban to their commitment”.

But Dame Barbara Woodward, the UK’s ambassador to the UN, said the militants would be judged “on the basis of their actions on the ground, not their words”.

Labour’s shadow foreign secretary Lisa Nandy welcomed the resolution but said it had left “questions unanswered that now need to be urgently addressed”.

Mr Raab told BBC Radio 4’s Today programme that officials could not be “definitive” when it came to the number of people who remained in Afghanistan, but the number of UK nationals was in the “low hundreds”.

Others still there included people covered by the Afghan Relocations and Assistance Policy (Arap), who worked for the UK government, and about 250 special cases such as journalists, judges, women’s rights activists and Chevening scholars, he said.

The final flight for US troops left the capital, Kabul, shortly before midnight local time, meeting President Joe Biden’s commitment to withdraw by 31 August.

Afghan journalist Bilal Sarwary, who fled the country with his young family and just one change of clothes, said ordinary people in the country faced a “very uncertain future”.

He told BBC Breakfast that thousands of people were queuing outside banks in Kabul, and could only withdraw $200 (£145) a week, which was “not enough” to buy food, cooking supplies and other items.

Mr Sarwary also warned there was a “risk of famine” as Afghanistan – which he said relied heavily on imported foods like rice and wheat – remained shut off from other countries.