KABUL, Afghanistan -- Afghan President Hamid Karzai has again accused the United States of killing civilians in a drone airstrike, this time in a Nov. 20 attack on a border area between two eastern provinces where Taliban insurgents maintain strongholds.

In a statement released on his presidential website late Wednesday night, Karzai condemned the United States for an alleged drone strike that he said killed seven civilians, including women and children, in Nuristan province on the border with Kunar province near the Pakistan frontier.

Karzai has cited U.S. and coalition attacks that inadvertently kill civilians as justification for refusing to sign a proposed 10-year security agreement that would define Afghanistan’s relationship with the United States after combat troops withdraw next year.  Though the United Nations blames insurgents for three-quarters of civilian casualties here, Karzai rarely condemns the Taliban for suicide bombings and roadside bomb attacks that indiscriminately kill civilians.

The U.N.-led International Security and Assistance Force, or ISAF, immediately responded with a statement acknowledging an airstrike in the Kunar area on Nov. 20, but denying that any civilians were harmed. The statement said the attack targeted "known Al Qaeda Arab and Taliban leaders," killing six "terrorists and insurgents."

"We have no evidence of civilian casualties related to this operation," ISAF said, adding that the mission was "carefully executed to avoid civilian casualties or damage to Afghan homes."

ISAF does not normally specify whether airstrikes are conducted by conventional or drone aircraft. American and British forces in Afghanistan operate armed drones, known in the military as RPVs, or remotely piloted vehicles.

Karzai said he met Wednesday at the presidential palace in Kabul with relatives of the alleged "martyred civilians." His Pashto-language statement said the relatives expressed support for Karzai’s demand that the U.S. end all ground raids on Afghan homes and villages as well as airstrikes that result in civilian casualties.

The statement quoted a family representative, Mawlavi Abdul Akbar, as telling Karzai:

"We are living under threat because of the drones. We can’t go out for prayers. We can’t go out of our homes. They [American troops] have blocked our way. We have brought our complaints to you as our sympathetic father to rid us of this disaster."

The statement appeared intended to bolster’s Karzai’s contention that U.S. and coalition forces show disregard for civilians -- and to publicly back up his conditions for signing the security accord.

On Tuesday, six civilians were killed and 13 wounded in two insurgent bombings in southern Afghanistan. On Monday, a Taliban suicide truck bomber detonated explosives at a government district center in eastern Afghanistan that killed four Afghan police officers and wounded 17.

Karzai made no public statement condemning insurgents for the three attacks, and he did not report meeting with families of any of those killed.

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Special correspondent Hashmat Baktash contributed to this report.