A roadside bomb planted by suspected Taliban insurgents killed 15 civilians travelling in a pick-up truck in the restive southern province of Helmand, a government official said Saturday, reported dpa.
Meanwhile, a suicide bomber in northern Afghanistan injured eight people on Saturday, while a blast in the southern province of Kandahar injured four policemen and two civilians.
NATO also said Saturday it was looking into the deaths of seven security guards allegedly killed by foreign troops elsewhere in the country.
Daoud Ahmadi, spokesman for the provincial governor of Helmand, said the attack which killed 15 civilians happened on Friday afternoon in the remote district of Khan Neshin, one of the most violent and restive districts in the province.
"A mine which was planted by the Taliban detonated and blew up a pick-up truck carrying civilians. As a result, 15 were killed and several others injured," Ahmadi said, adding there were no women in the trucks but could not confirm if there were any children.
In another incident, a suicide bomber detonated an explosive-laden vehicle close to an army base in the northern province of Kunduz on Saturday, injuring five soldiers, a police official said.
The bomber died in the blast and three women in a nearby house were also injured, Char Darah district police chief Gholam Muhaiyudin said.
The bomber used a police vehicle that local militants had stolen recently, he said.
Separately four police officers and two civilians were injured Saturday in a car bombing in the southern Afghan province of Kandahar, a government spokesman said.
An explosive-filled vehicle was abandoned inside a government parking lot in the centre of the provincial capital - also named Kandahar - Zalmai Ayoubi, spokesman for the provincial governor said.
Five police vehicles and several civilian cars were damaged in the blast, the Interior Ministry in Kabul said in a statement.
Roadside bombs, still killer number one according to NATO, are effective tactics used by the Taliban as part of their insurgency, causing most of the fatalities among Afghan and international troops.
Most civilian causalities are also caused by roadside bombs. More than 2,400 civilians have died this year, the highest number of casualties since the US-led invasion ousted Taliban in 2001.
Meanwhile, NATO said Saturday it was looking into allegations that seven members of a private security firm had been killed by foreign troops in south-eastern Afghanistan.
The incident happened in Rohani Baba, a village in Paktia province on early Saturday, Abdul Rahman Mangal, the deputy provincial governor said. An unknown number of private security forces were killed by the NATO troops, he alleged.
The NATO-led led International Security Assistance Force (ISAF) confirmed in a statement that its forces, backed by Afghan troops, had killed seven armed individuals during an anti-insurgent operation.
The combined forces encountered a group of armed men inside a vehicle after they detained a suspected arms dealer near Gardez, the provincial capital, it said.
One of the men got out of the vehicle and was shot dead by the joint forces after being assessed as "hostile," the statement said, adding, "Multiple other armed individuals then engaged the force, which resulted in a total of seven individuals killed."
ISAF said it was assessing "who the individuals were, why they were armed and why they were in that area at that time of the morning."
Dozens of people took to the streets in Gardez city later on Saturday, chanting anti-US and Afghan government slogans, the BBC reported.
The demonstration turned violent when the mob began throwing stones at police, who were trying to disperse the protesters, the report said, adding that one policeman and seven demonstrators were injured.
Nearly 150,000 international forces are currently fighting the Taliban insurgency in Afghanistan. Night raids have become a major area of contention between international forces and Afghan President Hamid Karzai, who has long been publicly critical of the amount of civilian casualties during night operation.
Karzai in a newspaper interview last month said he and his people were getting impatient with a war that had been going on for nearly a decade, and in particular wanted to see "an end to nighttime raids by foreign troops on Afghan homes."