Taliban insurgents marked the start of their spring offensive on Sunday by claiming responsibility for a remote-controlled roadside bomb blast that killed three police officers.
In past years, spring has marked a significant upsurge in fighting between the Taliban and NATO forces along with their local allies. This fighting season is a key test, as the international coalition is scheduled to hand over security responsibilities to Afghan forces next year.
In Sunday's attack in Ghazni province in southern Afghanistan, a bomb exploded under police vehicles traveling to the district of Zana Khan to take part in a military operation against insurgents, Mohammad Ali Ahmadi, the province's deputy governor, told The Associated Press.
He said the blast destroyed the vehicle carrying Col. Mohammad Hussain, the deputy provincial police chief, killing him and two other officers. Ahmadi said two officers also were wounded in the insurgent operation, which he said clearly targeted Hussain.
Taliban spokesman Zabiullah Mujahid claimed responsibility in an email sent to news media. He called the bombing the first attack in the Taliban spring offensive.
April already has been the deadliest month this year for attacks across the country, where Afghan security forces are increasingly taking the lead on the battlefield in the war that has lasted more than 11 years.
Insurgents have escalated attacks recently in a bid to gain power and influence ahead of next year's presidential election and the planned withdrawal of most U.S. and other foreign combat troops by the end of 2014. US-backed efforts to try to reconcile the Islamic militant movement with the Afghan government are gaining little traction.
There are about 100,000 international troops in Afghanistan, including 66,000 Americans. A top priority of the US force, which is slated to drop to about 32,000 by February 2014, is boosting the strength and confidence of Afghan forces.
Also Sunday, the US Air Force said the coalition plane that crashed on Saturday in southern Afghanistan, killing four service members, was a MC-12 Liberty aircraft.
The twin-engine turboprop plane provides intelligence, surveillance and reconnaissance, or direct support to ground forces. It crashed in Zabul province, about 180 kilometers (110 miles) northeast of Kandahar Air Field, the Air Force statement said.
The four Air Force service members were deployed to the 361st Expeditionary Reconnaissance Squadron with the 451st Air Expeditionary Wing at Kandahar Air Field, the statement said. Their bodies were recovered. The cause of the crash is under investigation, but NATO has said initial reports indicate there was no enemy activity in the area where the plane went down.
Taliban has named its spring offensive after Khalid ibn al-Walid, a companion of Islam's Prophet Muhammad who became a legendary Muslim military commander known as the "Drawn Sword of God." The insurgents said their forces planned to infiltrate enemy ranks to conduct "insider attacks" and target military and diplomatic sites with suicide bombers.
In the eastern province of Nangarhar, two local officials said insurgents attacked a US convoy as it passed through two nearby villages on Sunday and that four Afghan civilians were killed in the crossfire when the soldiers fired back.
The US-led international military coalition said it was investigating reports of civilian casualties in the province on Sunday but could not immediately confirm them.
The coalition also said Afghan and foreign forces arrested six insurgents on Sunday — three in Helmand province, one in Baghlan province and two in Kandahar province. The report said the two taken into custody in Kandahar city included a local Taliban leader who allegedly coordinated assassinations, sniper ambushes and other attacks against coalition and Afghan forces.