A spokesman for the provincial governor said a security personnel supervisor was among those killed.
Hours earlier, a bomb hidden in trash ripped through the office of acting governor of neighboring Khost province, wounding him and several other senior officials, while Afghan security forces killed two would-be suicide bombers in Khost.
Meanwhile, a top al-Qaida commander in Afghanistan called last week's suicide bombing on the U.S. base in Khost that killed seven CIA officers revenge for three militant leaders killed in drone strikes in Pakistan.
In a posting on an al-Qaida-linked Web site late Wednesday, Sheikh Mustafa Abu al-Yazid said the attack was a retribution for the death of the former Pakistani Taliban leader Baitullah Mehsud and two top al-Qaida commanders, Abu Saleh al-Somali and Abdullah Saeed al-Liby.
It was unclear if the al-Qaida statement was claiming responsibility for carrying out the bombing. Both the Afghan and Pakistani Taliban have already said they were behind the attack.
Intelligence officials say the bomber, Humam Khalil Abu-Mulal al-Balawi, was a Jordanian informant working as an al-Qaida double agent.
In other news, hundreds of demonstrators chanted anti-U.S. slogans and burned an effigy of U.S. President Barack Obama in the eastern city of Jalalabad. The demonstrators blame U.S. soldiers for a Wednesday roadside bombing near the city that killed four Afghan children and a policeman.
Elsewhere Thursday, several U.S. lawmakers, including Senator John McCain, visited the Afghan capital, Kabul.
McCain voiced his support for the U.S. military strategy in the region, including the use of drones to target militants, saying they have knocked al-Qaida and other Islamic extremist groups "off-balance."