President Joe Biden, his voice breaking with emotion, has vowed the US will hunt down those responsible for twin explosions at the Kabul airport in Afghanistan.

Mr Biden asked the Pentagon on Friday morning (Australian time) to develop plans to strike back at those responsible.

The blasts killed at least a dozen American troops and scores of civilians in what was the worst day of casualties for US forces there in a decade.

Islamic State Khorasan (ISIS-K), an affiliate of militants who previously battled US forces in Syria and Iraq, claimed responsibility for the attack.

“We will not forgive, we will not forget. We will hunt you down and make you pay,” Mr Biden said in remarks at the White House.

He promised US evacuations would continue, but gave no indication of a change to Tuesday’s US pullout target.

“I have also ordered my commanders to develop operational plans to strike ISIS-K assets, leadership and facilities. We will respond with force and precision at our time, at the place we choose and the moment of our choosing,” Mr Biden said.

Later, Prime Minister Scott Morrison also denounced the deadly blasts in Kabul.

“Our hearts sank when we heard this news,” he said.

“Australia condemns the evil, the calculated and inhuman attacks that were undertaken in Kabul overnight on the innocent and on the brave. We join with our American and Afghan friends in morning their terrible and awful loss.

“I have conveyed Australia’s and my own personal deep sadness for the loss of those brave American souls, to the President of the United States, by letter this morning. They have fallen in a very worthy cause.”

Mr Morrison said Australia had evacuated 4100 people from Kabul – “one of the most dangerous places on Earth” – in the past nine days. The life-saving mission couldn’t have been done without the US and Britain, he said.

Australia has halted all evacuations from Afghanistan, with the last troops leaving late on Thursday, just hours before the twin explosions.

“Our plan now moves into its post-evacuation stage – and that involves ensuring that we start the process of returning, through our official humanitarian program, people to Australia,”he said.

Foreign Minister Marise Payne also condemned the attacks, and repeated official advice for any Australians remaining in Afghanistan not to travel to Kabul’s airport.

“There is an ongoing and high threat of terrorist attacks,” she said.

“If you are in the vicinity, move to a safe location and provide contact details for consulate support.”

No Australian troops or officials were injured in Thursday’s blasts. Senator Payne said she could not confirm if any Australian citizens or residents had been hurt.

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Earlier, Mr Biden appeared to fight back tears and his voice cracked with emotion as he talked about the American “heroes” who died.

“It’s been a tough day,” he said.

Mr Biden said he told the US military that he would grant additional force if they needed it: “Whatever they need, if they need additional force, I will grant it.”

He defended his handling of his most serious foreign policy crisis, saying ultimately it is his responsibility, while assigning some blame to his predecessor, Republican Donald Trump, for the 2020 agreement Trump negotiated with the Taliban.

“I bear responsibility for, fundamentally, all that’s happened of late,” Mr Biden said when asked if he was responsible for the events of the past two weeks.

He said he did not trust the Taliban but believed it was in the group’s interest to let the evacuations continue.

Mr Biden had been warning of the possibility of attacks before the blasts erupted at the Kabul airport.

“I know of no conflict, as a student of history, no conflict when a war was ending one side was able to guarantee that everyone who wanted to be extracted from that country was able to get out,” he said.

-with AAP