A roadside bomb killed 10 labourers and wounded 28 on Tuesday as they were driving to work to clean streams in southern Afghanistan, officials said. Separately, an Afghan deputy intelligence chief escaped an attempted suicide bombing claimed by the Taliban in the nation's capital.

The roadside bomb tore through a truck carrying the workers through restive Kandahar province, said Dr. Qayoum Pakhla, the director of Kandahar Hospital. The local government in the region employed the men to work cleaning rivers and streams there.

"I could see people calling for help and crying," said one of the survivors, who gave his name as Sabdullah. "I saw some of my friends' dead bodies. I was helpless at that moment."

There was no immediate claim of responsibility for the attack, which comes as insurgents in Afghanistan recently started their spring offensive.

Meanwhile, Ahmad Ziad, a deputy chief at the National Directorate for Security, was unharmed in an attempted suicide bombing that targeted his convoy as he was travelling to work on Tuesday morning, Kabul police said.

Ziad's bodyguards opened fire on a suspicious sport utility vehicle that was coming at the convoy, wounding the driver and stopping the speeding SUV laden with explosives, the police said.

The driver was arrested and hospitalized under guard, pending an investigation. Taliban spokesman Zabiullah Mujahid claimed responsibility for the attempted bombing in a message to The Associated Press.

The attacks came after the Afghan intelligence agency said Monday that the reclusive leader of the Afghan Taliban has disappeared from a suspected hideout in Pakistan and has been out of contact with his commanders for days — adding further questions about Mullah Mohammad Omar after a media report said he has been killed.

The Taliban denied the claim on the Afghan news channel Tolo that Omar was shot dead while being moved inside Pakistan with the help of a former Pakistani intelligence official. A Taliban spokesman countered that Omar was alive and was somewhere inside Afghanistan.

The conflicting reports, however, underscore the complicated disputes and suspicions between Afghanistan and Pakistan as the U.S. intensifies pressure on both sides: urging Afghan forces to step up efforts against militants and pushing Pakistani authorities to help unravel the networks that aided Osama bin Laden.

Pakistan's foreign minister, meanwhile, was in Kabul for talks with Afghan President Hamid Karzai, who has been increasingly outspoken in the need for Pakistan to take a stronger role in the fight against militant groups. Trilateral talks on security were scheduled to begin Tuesday between Afghanistan, Pakistan and the United States.

There also has been much speculation that the U.S. might ramp up efforts to kill or capture the Taliban leader after the raid that killed Osama bin Laden on May 2 in neighbouring Pakistan. President Barack Obama has said he would order another covert military raid if it was necessary to stop terrorist attacks.