(CNN) A bomb ripped through an Afghan national army bus in the capital city of Kabul, killing at least 27 people and injuring 29 others Saturday morning, Interior Ministry spokesman Zmarai Bashary told CNN.
Most of the dead and wounded were soldiers, but civilians were also among the casualties, he said.
No group has has taken responsibility for the attack, Bashary said.
Afghan President Hamid Karzai called the attack "an act of extreme cowardice."
"No doubt someone that did this was against people, against humanity, definitely against Islam," Karzai said. "A man who calls himself Muslin would not blow up innocent people in the month of Ramadan."