Nato has said that the Taliban committed the strike, while the Taliban have said that Nato are behind the attack.
James Bays, Al Jazeera's correspondent in the capital Kabul, said: "Certainly we know what happened which is a very large explosion ... But we have no idea who was behind it.
"The Taliban say they are not responsible, saying they deplore it and condemn it in the strongest terms."
Hamid Karzai, the Afghan president, condemned the attack, saying that was "against the whole of humanity".
Our correspondent said that Arghandab was once a fertile, agriculturally rich area, but it has changed to region of conflict in recent years, particularly in the last three years.
"It is an area that Nato concentrates on as they continue their operations in the Kandahar area," he said.
Toror Yalai Wesa, the governor of Kandahar, told Al Jazeera that a survivor had said a car bomb was the cause of the explosion.
"We don't have any women casualties. Most of them are adult men and some are young children," he said.
The man getting married was a policeman from one of the checkpoints in the area, Wesa said.
Mohammad Zanif, the groom's brother, told the AFP news agency that the groom had been wounded.
"There was an enormous explosion and as a result everyone there was either killed or injured," he said.
Relatives of the wounded gathered at an area hospital and local television appealed for people to donate blood to help treat the injured.
Focus of build-up
Kandahar is the focus of a build-up by US-led military forces trying to push back the Taliban and the US has previously said that they are planning a major operation in the area soon.
However, Stanley McChrystal, the chief US and Nato commander in Afghanistan, said on Thursday that the operation would now happen more gradually.
"Nato has, for a long time, told us that there is going to be this be operation around now, in June," Al Jazeera's Bays said.
"But it looks like it is not going to happen as a major operation now. One reason is the Afghan government has major concerns over a major operation.
"And because things aren't going well in Helmand and the US military is putting a lot of resources there because there is a lot of Taliban activity there.
"We do know that there is a lot of special forces' activity there which they don't talk about so much and a lot of Taliban activity who are trying to take out senior government figures."