In the day's second major attack, a roadside bomb targeting a police convoy in southern Afghanistan killed three civilians and wounded 13 others, the local police chief said.
 
Hostage video
 
Also on Thursday, a German engineer held hostage by the Taliban appealed for help in a video broadcast on a private Afghan television station, which showed him slumped over and coughing.

An Afghan TV station aired the latest video
appeal by Blechschmidt for help [AFP]
Speaking with apparent difficulty, Rudolph Blechschmidt, 62, said in  German that he was a prisoner and in poor health.
 
He urged the Afghan government and German embassy to do all they could to secure  his release.
 
Blechschmidt was kidnapped in southern Afghanistan on July 18, one day before a group of South Korean aid workers were also abducted.
 
The hostage video was aired against a backdrop of Taliban resurgence across the country.
 
Nato base attacked
 
On Wednesday, anti-government fighters wearing Afghan army uniforms attacked a Nato base in Nuristan, killing two Afghan soldiers and wounding 11 Nato soldiers, according to a multinational-force statement.
 
Nuristan is a mountainous province in the country's northeast.
 
The raid "resulted in two Afghan  National Army (ANA) soldiers killed and 11 ISAF soldiers wounded", the Nato-led International Security Assistance Force (ISAF) said in a statement.
 
"The Taliban extremists who attacked were wearing ANA uniforms, which allowed them to approach the base."
 
US Major Christine Nelson-Chung, an ISAF spokeswoman, said several Taliban fighters were killed in the attack but could not give a precise figure.
 
Escape for governor
 
In a separate incident on Wednesday, a suicide bomber attacked the convoy of a senior provincial official, killing four people and wounding eight others.
 
Arsala Jamal, the governor of Khost, a southeastern province, escaped unharmed.
 
The dead include at least three of his bodyguards.
 
The attack occurred close to a base for Western soldiers just outside Khost.