Violence in Afghanistan has surged, with 2009 being the worst year since U.S.-backed Afghan forces overthrew the Taliban in 2001. More than 2,400 civilians were killed last year, a 14 percent rise on 2008, the United Nations said.
In the first incident, a suicide bomber driving a three-wheeled rickshaw detonated his explosives near a crowd who were holding a picnic for the Afghan New Year in Gereshk district of Helmand province, the provincial governor's spokesman said.
"The target was an Afghan Army vehicle. The first reports are that 10 civilians have been killed and seven more wounded," said spokesman Daoud Ahmadi, adding the bomb missed its target.
A witness at the scene told Reuters by telephone he had been no more than 50 meters away from the blast.
"The bomber was driving a rickshaw and was targeting an army vehicle. When the soldiers saw the rickshaw they sped up. The bomb exploded in a crowded area where many people were having picnics," said Khan Mohammad.
"Many people have been killed and wounded," he said.
A spokesman for NATO-led forces in Kabul said none of its forces were killed or wounded in the attack, but that foreign troops were now in the area assessing the situation.
In February, thousands of U.S. Marines launched an assault in Marjah, another part of Helmand, which had been under the insurgents' control. The operation was described as the biggest offensive of the eight-year war.
There are some 120,000 foreign troops in Afghanistan and that is set to rise to nearly 150,000 by the end of this year as Washington sends in more troops as part of a new strategy to try and quell the mounting violence.
Separately, in Khost province in the southeast of the country, a roadside bomb killed two Afghan civilians and wounded four, a senior police chief said.
"A civilian car hit a roadside bomb on the outskirts of Khost city. Two civilians were killed and four wounded," acting provincial police chief Mohammad Yaqoub Mandozai told Reuters.