At least 27 people, including the mayor of an Afghan city, have been killed in a spate of attacks, officials have said.

In the deadliest attack on Monday, 12 civilians - four women, two children and six men - were killed by a roadside bomb that exploded as they drove in a tractor in the Shamolzai district of southern Zabul province, Mohammad Wazir, the district chief, said.

"This was a mine newly planted by the Taliban," he told the Reuters news agency.
   
Taliban fighters later ambushed a convoy of a security firm in another area of Zabul, killing six Afghan security guards and two civilians nearby, Ghulam Jailani, a senior provincial police official, said.

Earlier on Monday, Mohammad Rahim, the mayor of Mehterlam, was among seven people killed by a teenage suicide bomber who blew himself up at the gate of a municipal administration building in the eastern province of Laghman, the interior ministry said.

Teenage bomber
   
Three body guards and three civilians were killed along with the mayor.
   
Sayed Ahmad Sopai, a spokesman for the provincial governor's office, said 10 people were also wounded, including three women.

He said the suicide bomber was identified as a 14-year-old boy from Paktika province further south.
   
The Taliban have frequently used suicide bombers to strike government buildings as part of their campaign to drive foreign forces from Afghanistan.
   
The group has extended the size and scope of its activity and has carried out a number of high-profile attacks in major cities since last year.
   
To fight the Taliban, the United States plans to more than double its forces in Afghanistan this year, from 32,000 at the start of the year to a projected 68,000 by year's end.

Other Western countries have about 30,000 troops in Afghanistan.