Hundreds of angry protesters gathered outside the American consulate in Karachi on Sunday, as Pakistan held funerals for the 24 soldiers killed Saturday in a NATO cross-border airstrike in the country's northwest.

Reporters near the consulate say at least 700 people were outside the heavily fortified compound shouting “Down with America” and other anti-American chants.

Meanwhile, the nation's army chief was among those attending funerals of the victims. Their coffins, draped in green and white Pakistani flags, are being airlifted to their respective hometowns.

NATO and U.S. officials responded quickly to try to minimize the repercussions of the attack on the Pakistani military outposts. NATO chief Anders Fogh Rasmussen said Sunday he has offered his condolences to Pakistan's Prime Minister Yousuf Raza Gilani for what he called the “tragic, unintended” deaths.

Rasmussen said he told the prime minister the deaths of the Pakistani troops was “as unacceptable and deplorable as the deaths of Afghan and international personnel.” He said he supports the NATO investigation that is under way.

Earlier Sunday, Pakistan's Foreign Minister Hina Rabbani Khar told U.S. Secretary of State Hillary Clinton the air raid was not acceptable and demonstrated a complete disregard for human life. Clinton responded by saying she was deeply saddened, and she promised to work with Pakistan on the issue.

Pakistan reacted swiftly to the airstrike by shutting down all NATO supply lines through its territory to Afghanistan and ordering the U.S. to vacate an air base in southwestern Baluchistan province within 15 days.

Prime Minister Gilani and top leaders said Saturday the Pakistani government “will revisit and undertake a complete review of all programs, activities and cooperative arrangements with US/NATO/ISAF.” They called for “strong and urgent action” against those responsible for the deadly incident.

Pakistan also is reexamining its decision to attend a major Afghanistan peace conference in Bonn next month.