A car packed with explosives exploded on Tuesday as it was passing by a crowded market in Afghanistan's eastern province of Paktika, killing at least 30 people and wounding 40, police said.
"Right now, police are taking all the wounded to hospitals," a local deputy police chief, Nissar Ahmad Abdulrahimzai, told Reuters.
Officials said the death toll was certain to rise. Another source said up to 50 people may have been killed.
The attack took place not far from the porous border with Pakistan's North Waziristan region, where the military has been attacking hideouts of the Pakistani Taliban in the past few weeks, prompting militants to retreat towards Afghanistan.
Abdulrahimzai said police had been tipped about the car and were chasing it when it exploded.
"The explosion was so big it destroyed many shops. Dozens of people are trapped under the roofs," Mohammad Raza Kharoti, the district governor, told Reuters.
"The number of wounded will rise to more than 100 and the number of those martyred will also increase."
In Kabul, a remote control bomb concealed by a roadside killed two employees of President Hamid Karzai's media office and wounded five, police said. The Taliban claimed responsibility.
The attacks took place as foreign troops are gradually withdrawing from the country. The United Nations said last week civilian casualties jumped by almost a quarter in the first half of this year as hostilities escalate.