"We don't at this stage know the final numbers for dead and wounded but it is clear this attack is among the worst that Kabul has seen," Secretary-General Ban Ki-moon's Special Representative Tom Koenigs said in a statement.

The attack, which took place on a busy city street, was undoubtedly aimed at terrorizing the population, he noted.

"Those responsible are evidently incapable of offering anything beyond savagery and murder. They must be made to know they will not prevail."