A homicide car bomber detonated near a convoy of private security forces Saturday in southern Afghanistan, killing four Afghan guards and 11 civilians, including three women and two children, police said.

The bomb went off west of Kandahar city and also wounded six other guards as well as 20 civilians who were in two minivans passing by the convoy, said Kandahar provincial police chief Syed Agha Saqib.

Saqib said the guards worked for the U.S. Protection and Investigations security firm, but USPI could not immediately be reached for comment or to confirm that their employees were attacked.

Five women and three children were among the civilians wounded. Women's and children's shoes were scattered about the area. A stuffed animal toy was left in one of the destroyed minivans.

Violence in Afghanistan has risen sharply during the last two months. More than 3,700 people have died so far this year, most of them militants, according to an Associated Press tally of casualty figures provided by Western and Afghan officials.