A suicide car bomb exploded near a bank in Afghanistan on Saturday as police and soldiers queued for their wages, killing four including three children in the volatile south.

The blast happened in Lashkar Gah, capital of Helmand province, where Afghan forces took control of security from British troops last month as international forces started withdrawals across the country.

It came a few days before the start of Eid, the Islamic festival marking the end of the holy month of Ramadan.

Along with the dead, 21 people were wounded -- ten Afghan soldiers, five policemen and six civilians, a statement from the Helmand governor's office said.

"The martyred were two small boys, a small girl and a middle-aged man," it added.

"The target of the attack was police and army soldiers who gathered in front of Kabul Bank to take their monthly salaries."

No-one has so far claimed responsibility for the attack, although the Taliban have carried out similar strikes in the past targeting government employees collecting their pay.

Ismail Khan, an official at Lashkar Gah police headquarters, said that a seven-year-old girl was among the dead.

Deputy police chief Kamaluddin Sherzad added that the scene of the blast was close to the heavily-secured Helmand governor's office.

Meanwhile, in the neighbouring province of Kandahar, one person was killed and 22 were injured in two car bomb blasts near police posts in the city. A total of 13 children were among the wounded, provincial officials said.

Both attacks were strongly condemned by President Hamid Karzai in a statement released by his office.

Southern Afghanistan, traditionally a stronghold of the Taliban, has been the focus of international troop operations in recent years. Kandahar is seen as the birthplace of the Taliban.

Although government officials are frequently targeted, civilians are the biggest victims of the ten-year, Taliban-led insurgency.

Figures released last month by the United Nations showed that the number of civilians killed in the first half of the year in the Afghan war rose 15 percent.

It added that insurgents were responsible for 80 percent of the killings.

The Lashkar Gah attack is the latest to strike the city in recent weeks since Afghan forces assumed formal responsibility for its security.

The handover was part of the first wave of a transition process which will eventually see all foreign combat forces leave Afghanistan by the end of 2014.

Lashkar Gah was deliberately chosen in the initial group of seven places around the country to prove that Afghan security forces could hold their own, Western diplomats have said.

But some residents believe security has deteriorated since the handover, raising questions about the transition process.

Karzai is set to announce in late September or October which places will be next to transition.

Since British troops formally handed control of security in Lashkar Gah to the Afghan army on July 20, there have been several attacks.

These included a suicide car bomb attack on the town's police headquarters which killed 12 policemen and a child on July 31.

And in a macabre incident the day before the transition ceremony, seven police were poisoned and then shot dead by insurgents.

Some local officials have accused the Taliban of deliberately trying to destabilise the city and spread fear in the wake of the transition process.

There are presently around 140,000 foreign troops in Afghanistan supporting Karzai's government, the majority from the United States, although they are all due to leave over the next three years.