KABUL, Afghanistan - A massive explosion rocked a highly secure diplomatic area of Kabul Wednesday morning, causing casualties and sending a huge plume of smoke over the Afghan capital. It was one of the worst attacks Kabul has seen since the draw down of foreign forces at the end of 2014, CBS News correspondent Debora Patta reports.

Afghanistan's Health Ministry told CBS News that the blast left more than 80 dead and 350 wounded, and that most of the casualties were civilians, including women and children. 

The U.S.-led NATO coalition, Operation Resolute Support, said in a statement that the bombing happened near its headquarters and the German Embassy.

It said, "Afghan security forces prevented the VBIED from gaining entry to the Green Zone, but the explosion caused civilian casualties in the vicinity."

"The attack demonstrates a complete disregard for civilians and reveals the barbaric nature of the enemy faced by the Afghan people," the statement continued. "It also highlights the hypocrisy of the enemy who claim that they only target Afghan Security Forces and Foreign forces, yet continue to cause death and suffering amongst innocent Afghans."

The German Foreign Ministry said German embassy workers were wounded in the blast, and that an Afghan security official who had been protecting the building was killed.

The Taliban on Wednesday denied involvement in the bombing. Both the Taliban and the Islamic State of Iraq and Syria (ISIS) have staged large-scale attacks in the Afghan capital in the past.

The explosion occurred at the peak of Kabul's rush hour when roads are packed with work time commuters, Patta reports.

The U.S. Embassy in Kabul warned American citizens to avoid the area of the blast and cancelled all its appointments for routine American Citizen Services for the day. 

Afghanistan president Ashraf Ghani's office condemned the "cowardly attack in the holy Month of Ramadan targeting innocent civilians in their daily life," while the U.S. Embassy Kabul Special Charge d'Affaires Hugo Llorens said, "This horrific and shameful attack demonstrates these terrorists' complete disregard for human life and their nihilistic opposition to the dream of a peaceful future for Afghanistan. The terrorists, and those who provide them support in any form, deserve the utter scorn of all civilized people around the world."

The Green Zone neighborhood is considered Kabul's safest area, with foreign embassies, press bureaus, and government offices protected by dozens of 10-foot-high blast walls and guarded by police and national security forces. 

The Associated Press contributed to this report.