**A roadside bomb in Afghanistan has killed at least 21 people as they were travelling to a wedding in the south of the country, officials say.**Helmand provincial police chief Assadullah Sherzad told AP news agency that women and children were among the dead in Garmsir district.
Officials say this is an area where roadside bombs are frequently used to attack foreign and Afghan forces.
Thousands of Nato troops are conducting offensives in Helmand.
Reports say those killed had been travelling on a tractor and a trailer.
At least five other people were injured, according to officials.
The incident happened on Wednesday, although information was not released until Thursday.
Afghan Gen Shir Mohammad Zazai said they were still gathering details about the blast.
Garmsir district is a militant stronghold where US Marines have been trying to flush out insurgents ahead of presidential and provincial council elections on 20 August.
The blast came as new Nato Secretary General Anders Fogh Rasmussen visited Afghanistan. He is now in the southern city of Kandahar.
Mr Rasmussen said on Wednesday he was determined to reduce civilian casualties in Afghanistan.