United Nations Secretary-General Ban Ki-moon has condemned a suicide attack on a U.N. convoy in Afghanistan that killed two Afghan doctors.

Taliban militants claimed responsibility for Sunday's attack, in which a suicide car bomber struck the convoy in the southern Afghan province of Kandahar.

The doctors killed in the blast in the town of Spin Boldak worked for the U.N.'s World Health Organization on a polio vaccination program. The attack also killed an Afghan driver employed by the U.N. and wounded about 15 other people.

Mr. Ban says the doctors were traveling in clearly-marked U.N. vehicles. The secretary-general says the bombing shows what he calls the "brutal face" of those opposing peace and reconstruction in Afghanistan.

In another incident on Sunday, six children were killed when a bomb they were playing with exploded in the central province of Ghazni.

Some information for this report was provided by AFP, AP and Reuters.