At least 23 civilians have been killed in southern Afghanistan, where a minibus and a tractor separately struck explosives in Helmand province, officials said.
The minibus was travelling from Nahr-e-Saraj district to the provincial capital of Lashkar Gah on Friday when it hit a mine and all 19 people inside were killed, said Kamaludden Sherzai, Helmand's deputy police chief.
"The mine was very powerful and destroyed the vehicle,'' said Sherzai. "They were all civilians. Some were children.''
When security forces arrived at the scene they were attacked by Taliban fighters, said Hekmatullah Akmal, a highway police commander.
He said the devastation caused by the blast made it difficult to determine how many people had been on the bus.
In Garmsir district, south of Lashkar Gah, a tractor also hit a roadside bomb, killing four civilians, officials said.
Violence against civilians is at a record high, with more than 1,400 Afghan civilians killed in the conflict this year, according to a recently released United Nations report.
Civilian deaths between January and June were up 15 per cent compared to the first half of 2010, due to roadside and suicide bombings, increased ground fighting and more deaths from air strikes.
The report said civilian deaths from roadside bombs alone increased 17 per cent this year from the same period in 2010, making roadside bombings the single largest killer of non-combatants.
Suspected Taliban and al-Qaeda fighters are responsible for 80 per cent of civilian casualties, with 14 per cent caused by NATO and Afghan forces, the report said.
Friday's blast came one day after coordinated bomb and suicide attacks in the neighbouring province of Uruzgan killed 21 people.
The Taliban, which claimed responsibility for Thursday's attack, first set off a motorcycle bomb, triggering five hours of fighting with security forces.
The violence comes at a critical juncture in the near decade-long conflict as thousands of US surge troops prepare to go home.
All foreign combat forces are due to leave Afghanistan by the end of 2014 and last week a first set of security handovers from NATO to Afghan forces took place in seven parts of the country.