Two bodies and seven injured men were taken to the Mirwais hospital after the blast, Dr Najibullah said.
ISAF headquarters in Kabul confirmed there had been an attack against its troops but said there were no military casualties.
Elsewhere, suspected Taliban fighters shot dead a district chief in western Afghanistan, while a senior policeman was killed at his home in the east, officials said on Thursday.
Aid worker seized
Separately, an Afghan aid worker and his driver were kidnapped by armed men. Abdul Zahir, chief of Gulran district in western Herat province, was shot dead in his car while travelling to Herat city, the provincial capital, on Wednesday, the interior ministry said.
One of his bodyguards was wounded, Dad Mohammed Rasa, a ministry spokesman, said. It was not clear whether the attackers were in vehicles or lying in wait at the roadside, he said.
Taliban blamed "The enemies of Afghanistan carried out this attack," Rasa told AFP, using the Afghan government's usual description for the ousted Taliban movement and its Muslim allies.
On Wednesday, armed men tried to kill Mohammad Mubeen, the chief of Barmal district in eastern Paktika province bordering Pakistan, but he escaped unharmed.
The attackers fled after Mubeen's bodyguards returned fire for several minutes, provincial governor Mohammad Akram Khpolwak said, also blaming the attacks on the Taliban.
Assailants believed to be Taliban shot dead a police investigations official on the same day at his home in the Zazi Maidan district of neighbouring Khost province, Abdul Hanan Raufi, the provincial police chief, said.
NGO staff snatched The regional chief of the Abn-i-Sina non-governmental organisation and his driver were snatched by unidentified armed men in Khost's Zurmat district, again on Wednesday, Raufi said.
The men were visiting a hospital that the aid group runs in the area. Also on Thursday, Pakistan's foreign minister, left for Kabul for talks on border security amid acrimony over alleged infiltration by Taliban fighters, officials said.
Khursheed Kasuri is to meet Rangeen Dadfar Spanta, the Afghan foreign minister, and Hamid Karzai, the president, in the Afghan capital, and will discuss proposed tribal councils, or jirgas, aimed at countering the Taliban influence in the region, the officials said.
Al Jazeera's correspondent in Pakistan, Kamal Hyder, said: "It remains to be seen whether the Pakistani foreign minister can convince his Afghan counterpart about the wisdom of talking to the insurgents rather than the military solution to defuse the problem.
He said: "The Taliban are becoming stronger of civilian casualties. Nato's task was rebuild and reconstruct, not to go after insurgents. But when when went after the insurgents, they ended up killing a lot of innocent civilians, and got caught in a quagmire. Now there is a threat of a major uprising and a strengthened Taliban."