A suicide bomber slammed into a bus in Kabul, killing at least 13 people Wednesday - the second such attack in the Afghan capital in as many days.
The Taliban claimed responsibility for the bombing, which occurred just as U.S. Defense Secretary Robert Gates wrapped up a two-day visit to the country to assess military efforts against rising militant attacks.
Afghan officials say among those killed in Wednesday's attack were six soldiers and seven civilians, four of them children.
Militant attacks on buses carrying military and government personnel have become increasingly common this year.
The Taliban also claimed responsibility for a suicide car bomb attack on Tuesday, which caused no deaths but wounded 22 Afghans.
Secretary Gates met Tuesday with Afghan President Hamid Karzai and his army chief Bismullah Khan. Both men told Gates that the Afghan military needs more trainers and equipment to fight the Taliban.
Gates said he would try to expedite the requests. He also expressed concern about increasing violence in Afghanistan, pointing out that the trend is - in part - connected to more aggressive efforts on the part of the United States and NATO to go after Taliban militants.
Some information for this report was provided by AFP, AP and Reuters.