KABUL, Afghanistan — As the Taliban opened a new front this week in the Afghan war by attacking American-backed aid organizations in Kabul, negotiators for the group and the United States were meeting in the latest round of talks on ending the war.

The Taliban has struck aid organizations sparingly in the past, making the attacks on Wednesday at the offices of CARE and Counterpart International even more stark. At least nine people were killed and 20 others wounded, Afghan officials confirmed. The death toll was nearly double initial reports.

A Taliban spokesman, Zabihullah Mujahid, was quick to claim responsibility for the attack and to offer an explanation on Twitter: Counterpart International, which works largely on civic engagement projects, is American led and is financed primarily by the United States Agency for International Development.

But neither Taliban nor American negotiators commented on the inherent contradiction in talking peace while attacking civilian targets. The Taliban had rejected pleas by the Afghan government and the Americans for a cease-fire during Ramadan, but they had promised to avoid civilian targets during the holy month.