The area, which is located near government offices, remained sealed off to traffic as police rescue teams were still searching for civilians trapped under rubble.

The blast destroyed dozens of houses, set alight a wedding hall and broke windows as far as one kilometre away.

The blast occurred as Kandahar residents had gathered at homes and restaurants to break their day-long fast. Like many Islamic countries, Afghanistan, where around 99 percent of the population is Muslim, observes the holy month of Ramadan from dawn to dusk.

President Hamid Karzai condemned the attack in a statement issued by his office Wednesday. It said the president held an emergency meeting with his security chiefs in Kabul and ordered them to find out facts surrounding the incident.

The blast occurred around one hour after the Afghan Independent Election Commission announced partial results of country's presidential election, which the radical Islamist Taliban had urged voters to boycott.

A partial vote count showed Karzai narrowly leading his former foreign minister, Abdullah Abdullah, by 40.6 percent to 38.7 percent, the Independent Election Commission said.

The commission released the results from about 10 percent of the polling stations from Thursday's election. There were around 28,000 polling stations around the country on election day.

The commission has said it expected to release the final results around Sep 17, but should the trend seen Tuesday continue, a run-off between Karzai and Abdullah would be necessary.