De Hoop Scheffer, speaking to reporters after talks with US President George W. Bush, lamented that North American Treaty Organisation forces had slain civilians in Afghanistan, calling it "always a tragedy."
"Let me say that when, in those actions of NATO, of those brave NATO soldiers, civilians are killed, as happened two days ago, that's always a tragedy. That's a tragedy," the secretary general said.
In their closed-door talks, de Hoop Scheffer and Bush discussed "the fact that the Taliban had begun using innocent civilians as human shields," said White House spokesman Tony Snow.
Snow later confirmed that the secretary general had explicitly described civilians killed in clashes on Tuesday as human shields seized by the Taliban: "That's what he said, yes."
Fourteen civilians were killed in a bomb blast in southern Afghanistan on Friday as the government said it believed around 25 were killed in fighting between NATO and the Taliban this week.
"Civilian victims are a tragedy, but we are there in favour of democracy. They are there to destroy democracy," the NATO chief told reporters in Bush's Oval Office.
Afghan President Hamid Karzai has called for improved co-ordination between Afghan and foreign troops to avoid civilian casualties.
Officials were trying to establish how many civilians were killed in clashes between NATO's International Security Assistance Force (ISAF) and Taliban insurgents in Kandahar province -- the birthplace of the religious movement.
The interior ministry in Kabul said around 60 people were killed in the battles late on Tuesday, and more than half were insurgents.
Ministry spokesman Zemarai Bashary said that about 25 of the dead appeared to have been civilians according to preliminary investigations.
An ISAF spokesman in Kandahar said it could confirm 12 civilians were killed in the skirmishes, which included a bombing raid. ISAF has already said it killed 48 insurgents.
Karzai on Thursday appointed a commission to investigate the civilian deaths, which came less than a week after he urged NATO forces to take more care after 20 other civilians were reported to have been killed.

Copyright AFP (Agence France-Presse), 2006