A suicide car bomber on Thursday killed 21 civilians in one of Afghanistan's deadliest attacks this year, while four NATO soldiers from Canada and 10 Taliban rebels died in other violence.
The interior ministry said a car bomber drove his vehicle into a crowded bazaar in southern Kandahar province.
"Twenty-one civilians, including children, were killed and 13 others were injured," ministry spokesman Yousuf Stanizai told the agency.
NATO said one of its convoys was a few metres away when the bomb exploded in Panjwayi district, but it was not affected.
The International Security Assistance Force (ISAF) convoy had been passing through to recover vehicles involved in two earlier roadside bombings that killed a Canadian soldier and wounded four others, spokesman Major Quentin Innes said.
"It was a suicide attack carried out by terrorists," Kandahar government spokesman Daud Ahmadi said. "Its target is not known as there were not any government or NATO present when it took place."
Panjwayi, a known Taliban stronghold, is about 30 kms west of Kandahar city.
The roadside bomb blasts were about 10 kilometres further west, in the Pashmul area.
The first bomb hit a patrol securing a major east-to-west highway at about 4:20 am, ISAF said. A Canadian soldier was killed and another wounded.
The second blast hit the same area around 7:15 am and wounded three more Canadian troops. None suffered life-threatening injuries.
Then around 12:30 pm another ISAF patrol was ambushed in the same area by insurgents armed with rocket-propelled grenades. Three soldiers were killed and six wounded, ISAF said, without immediately releasing their nationalities.
Later Canada's Defence Department in Ottawa said that three Canadian troops were killed in the ambush and six others wounded along with a local Afghan interpreter.
"I can confirm that three Canadian soldiers were killed and six others were wounded in a rocket grenade attack near Pashmul at 12:30 pm local time," Lieutenant John Nethercott said.
The latest deaths bring to seven the number of ISAF troops killed in southern Afghanistan since the force on Monday took over command of the area from a US-led coalition that unseated the Taliban in late 2001.
Three British soldiers were killed on Tuesday in neighbouring Helmand province when rebels attacked their convoy.
The NATO force in the south comprises nearly 8,000 ISAF troops -- including British, Canadian, Dutch and US soldiers.
Kandahar, where the Canadian troops are based, is a hotspot for suicide bombings. In the biggest this year, 22 civilians were killed when an attacker blew himself up among a crowd of men leaving a wrestling match in the border town of Spin Boldak in January.
Panjwayi, near where the fugitive leader of the Taliban Mullah Mohammad Omar once lived, has also been the target of major coalition strikes this year that have killed scores of rebels.
Afghan and international security forces are pursuing rebels in the south to establish government authority over the lawless area where Taliban fighters are said to have teamed up with drugs runners.
Ten rebels were killed late Wednesday when NATO warplanes helped Afghan security forces raid Taliban hideouts in Helmand's Garmser district, police said.
Two policemen were wounded, local police chief Mohammad Rasoul Aka said. Provincial police chief Mohammad Nabi Mullahkhil said 22 Taliban were killed or wounded.