Kabul reacted in despair and fear on Sunday, a day after a suicide bomb killed and wounded more than 250 people in the worst attack seen in the Afghan capital in months.

There was a mix of helpless anger at the seemingly endless wave of attacks after an ambulance packed with explosives blew up in a crowded city street, with security officials warning that more attacks were possible.

"How are we to live? Where should we go?" shopkeeper Mohammad Hanif, who was in his shop near the site of the explosion when it went off, told Reuters.

"We have no security, we don't have proper government, what should we do?"

At least 103 people were killed and hundreds more were wounded in the blast, claimed by the Taliban, a week after their deadly attack on the city's Intercontinental Hotel, in a calculated answer to US President Donald Trump's new strategy in Afghanistan.

After a deadly week in which an office of the aid group Save the Children in the eastern city of Jalalabad was also attacked, President Ashraf Ghani's Western-backed government has faced growing pressure to improve security.

Despite a major tightening in checks following the May 31 attack, the ambulance was able to get through the checkpoints, apparently without difficulty.

"People don't have work. There's no life for people in Afghanistan. People have to look for a life somewhere else, there's nowhere," shopkeeper Sameem told Reuters.

Saturday's attack, described as "an atrocity" by the head of the UN mission in Afghanistan, drew universal condemnation from neighbouring countries and allies who had expressed confidence that the new US strategy is producing results.