A suicide bomber on a motorcycle killed 10 civilians and two policemen in the first attack at a bazaar, while an intelligence official was among the dead in a second blast caused by a mine, which was claimed by the Taliban.
"At least 12 people were killed and more than 20 others wounded in a suicide attack in Kajake district of Helmand province," said the Afghan force coordination centre's Mohd Ismail Hotak.
An earlier report said seven policemen were killed.
Two hours later, a local intelligence official, two bodyguards and a civilian were killed in a mine explosion, said Daud Ahmadi, a spokesman for the provincial governor.
"The NDS (National Directorate of Security) deputy director of Nad Ali district, his two bodyguards and a civilian were killed today when a remote-controlled mine planted by the enemy exploded in Nad Ali district," he said.
The Taliban claimed responsibility for the second attack, while the first also bore the hallmarks of the Islamist movement.
General John Allen, commander of NATO's International Security Assistance Force (ISAF), said in a statement that ISAF personnel were among the wounded in what he called a "brutal" suicide attack.
"These attacks against the people of Afghanistan have no effect on the progress we are together making here with our Afghan partners and will only further isolate the Taliban from the process of peace negotiation," he said.
The Taliban, toppled in late 2001 in a US-led invasion, are waging an insurgency against the government and US-led forces, who have some 130,000 troops in the impoverished and war-ravaged country.
The hardliners announced earlier this month that they planned to set up a political office in Qatar, widely seen as a move towards peace negotiations with Washington and its Western allies.
A key US demand for any progress in negotiations is that the Taliban abandon violence and break with al Qaeda and other "terrorist" groups, Washington says.
"Mullah Omar (Taliban leader) has lost all control over Taliban insurgents, otherwise he would immediately denounce these attacks and order his 'forces' to stop attacking innocent Afghan civilians," Allen said.
"This latest act of violence further confirms that the insurgency has declared outright war on the people of Afghanistan and will stop at nothing to continue to use terrorism and intimidation to advance their own malign and selfish ends."
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