A suicide bombing in the Afghan capital Kabul on Wednesday killed eight people and wounded at least 28, officials said, in an attack on a convoy of armored personnel carriers used by the NATO-led Resolute Support mission.

The blast hit the NATO coalition convoy during the morning rush hour in one of the busiest areas of Kabul. Public health officials in the capital said eight civilians were killed and at least 25 wounded, with a number of civilian vehicles that were near the convoy destroyed or badly damaged. 

A Resolute Support Spokesman, U.S. Navy Captain Bill Salvin, said three U.S. service members were wounded in the attack. The armored personnel carriers, which are designed to withstand large blasts, were able to return to a coalition base under their own power, he said.

The attack follows a threat by the Taliban to target foreign forces in the spring offensive that it launched last week.

Witnesses said traces of blood and clothing could be seen on the ground at the blast site. Kabul television stations earlier reported that at least three people had been killed.

The heavily armored MRAP (Mine Resistant Ambush Protected) vehicles that coalition forces use to travel in Kabul appeared to have suffered only relatively minor external damage, witnesses said.

The attack comes three weeks after the US dropped its largest non-nuclear bomb, known as “the mother of all bombs”, on a tunnel complex used by IS in Afghanistan, reportedly killing many militants.

Meanwhile, the US is discussing whether to send more troops to Afghanistan, where militant groups have carried out numerous attacks recently.