Paktia is one of the regions in Afghanistan where the Taliban are at their most active, launching regular attacks on Afghan and foreign troops.
Elsewhere, armed groups attacked US-led multinational and Afghan forces less than 120 km northeast of Kabul, sparking a rare battle close to the capital.
In the northern Afghan province of Kunduz, three German soldiers and four civilians were killed in a suicide bombing on Saturday, Afghan security officials said.
The bomber struck as the soldiers patrolled the city of Kunduz, said General Nur Mohammad, chief of the Kunduz security department.
Four civilians also died in the blast and another 14 people, including two German soldiers, were wounded, another official said.
Also on Saturday, Abdul Wahab Safi, the security chief of Achin district in the province of Nangarhar, and his driver were killed in a remotely detonated explosion, Aljazeera's correspondent in Afghanistan quoted security officials as saying.
The Taliban claimed responsibility for the attack, saying that the blast killed six Afghan policemen, including the security chief, Al Jazeera said.
Battle near Kabul
The multinational force said on Saturday that Afghan and allied forces were on combat patrol late on Friday in the Asay Valley in Kapisa province, which borders Kabul province, where the capital is, when they were ambushed.
Abdul Satar Murad, the governor of Kapisa province, said about 20 fighters were killed, and that there were unconfirmed reports of civilian casualties.