A remote-controlled roadside bomb has killed at least nine Afghan civilians travelling on a bus just northwest of the capital, Kabul, local officials say.
Tuesday's explosion, which injured three others, flipped the bus onto its side in the Paghman district of Kabul province.
Colonel Amrullah Khan, the Paghman district police chief, said the man who detonated the device was arrested.
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"With the help of the local people, we were able to arrest the culprit, who had the remote control with him," he said.
Other police sources said the device was placed under a bridge and was detonated when the bus was above it at around 7am local time (02:30 GMT).
The driver of the bus, who survived the blast, also said the remote-controlled bomb exploded as the bus crossed the bridge.
Initial reports said the the bus was ferrying government employees to an Afghan ministry, but those reports could not be immediately be verified.
Khan said the blast killed nine people, including two who were rushed to a local hospital but died within hours. He said three others were wounded.
No group immediately claimed responsibility for the attack, but Khan blamed fighters affiliated with the Taliban.
A second blast at a Nato military base in Afghanistan's Logar province is reported to have injured at least 12 people.
According to the provincial police chief, a suicide bomber rammed the explosives-laden pickup vehicle into a gate at the base near Pule Alam, the provincial capital, on Tuesday morning.
"So far we have information that 12 civilians have been injured," Ghulam Sakhi Rogh Lewanai told the AFP news agency.
The spokesperson of the governor in Logar said those injured in the attack were civilian labourers working at the base.
The Taliban claimed responsibility for the blast.
"At around 9:00am (04:30 GMT) one of our mujahideen carried out a suicide truck bomb attack on a big US forces' camp resulting in many deaths and injuries," Taliban spokesperson Zabiullah Mujahid said in a text message.