KABUL An explosion outside a school south of the Afghan capital on Thursday killed at least 25 people, including 15 students, officials said, and Taliban fighters overran a district near the Pakistan border after heavy fighting.
The blast in Logar province and the gunbattles in eastern Nuristan were the latest incidents in an escalation of violence across Afghanistan since U.S. Marines launched a major new offensive in the Taliban bastion of Helmand a week ago.
That assault, Operation Strike of the Sword, is the first major operation under U.S. President Barack Obama's new regional strategy to defeat the Taliban and stabilize Afghanistan, which holds a presidential election on August 20.
Afghanistan's east and south have long been Taliban strongholds, although a growing insurgency has spread out of those areas in recent months to the relatively safer north and even to the outskirts of Kabul.
Officials said the Logar blast was caused by explosives hidden beneath a pile of firewood in the back of a truck which had crashed overnight, leading to speculation the explosives could have been meant for an attack elsewhere.
Logar police chief Ghulam Mustafa said the truck rolled into a stream between two schools. The blast went off as police checked the abandoned truck in the morning, he said.
"The four police who were checking the truck got killed, so were the students and some shopkeepers and other civilians," Mustafa told Reuters by telephone.
He said the explosives were possibly being taken by Taliban insurgents to Kabul for a planned attack there.
President Hamid Karzai condemned the blast as a "savage and anti-Islamic attack," the palace said in a statement.
It was the worst toll from a single blast since an attack on the Indian embassy in Kabul on July 7, 2008, killed 58 people.
In eastern Afghanistan near the border with Pakistan, which is fighting a growing insurgency of its own, Taliban fighters overran government buildings in Nuristan's Barg Matal district after heavy fighting, the provincial police chief said.
Officials in the area had pleaded for reinforcements after Taliban fighters surrounded key buildings on Tuesday, when eight police were killed and eight abducted during gunbattles.
The fighting flared again on Thursday and police were unable to hold the insurgents off, provincial police chief Mohammad Qasim said. The Defense Ministry in Kabul had promised to send 130 soldiers to Barg Matal to help hold off the Taliban.
"We have not received any reinforcements so far and the district fell into Taliban hands," Qasim told Reuters.
Nuristan senator Noor Rahman said it appeared some police had left their posts overnight.
One police commander and other officers had joined Taliban fighters to help them take over the district, he said.
The Marines launched the Helmand offensive last week with insurgency violence at its highest since the austere Islamist Taliban government was ousted by U.S. and Afghan forces in 2001.
While there have been no major engagements in Helmand in the past week, Afghan civilians and troops and foreign soldiers have been killed in a variety of attacks across the country.
About 20 foreign soldiers, most from the United States and Britain, have been killed in the past six days, making it one of the bloodiest weeks for foreign troops for many months.
On Thursday, the NATO-led coalition said another two soldiers were killed by a roadside bomb in the south.
Brigadier General Lawrence Nicholson, commander of the Marine Expeditionary Brigade in Afghanistan, told reporters in Washington overnight his forces had met only light resistance.
One of the main goals of the new operation is to capture ground from the Taliban and then hold it, something overstretched British-led NATO troops have so far been unable to achieve. It is also seeking to win over Afghans from the insurgency.
But Nicholson said the Helmand offensive has too few Afghan troops, making it difficult to achieve that latter goal.
"What I need is Afghan troops," he said in an audio link from Afghanistan. "I've got 4,000 Marines in the field and about 600, 650 Afghans. You can do the math."
(Additional reporting by Sayed Salahuddin and Jonathon Burch in KABUL, Rafiq Sherzad in JALALABAD, and David Morgan in WASHINGTON; Editing by Sugita Katyal)