Three suicide bombers killed 23 people and wounded dozens more in an attack on a construction firm in Afghanistan's restive southeast, government officials said on Monday, with the Taliban claiming responsibility for the assault.
Violence across Afghanistan has spiralled in the past year, with Taliban-led militants stepping up their fight against the Afghan government and its Western backers as Kabul prepares to take over responsibility for security gradually from foreign forces.
An Interior Ministry statement said the attackers forced their way into the firm's compound after killing a security guard and then detonated a truck packed with explosives.
A statement from the office of the Paktika governor said 23 people were killed and another 53 wounded. Earlier estimates said between 13 and 20 had been killed.
President Hamid Karzai condemned the attack, describing it as "brutal" in a statement released by his office.
Mohebullah Sameem, governor of southeastern Paktika province, earlier put the death toll from the attack in the remote Bermel district at 13.
He said the dead and wounded included employees of the firm and other civilians. Construction crews and others working on infrastructure projects are frequently targeted by insurgents.
Mukhlis Afghan, governor Sameem's spokesman, said the firm was one of the largest construction companies in the province funded by the U.S. government.
He said the blasts were so powerful that doors and windows were blown out of nearby houses, but he did not know if there were casualties outside the firm's compound.
Bermel shares a long border with lawless areas of neighbouring Pakistan, where insurgents are said to have safe havens from which they launch attacks inside Afghanistan.
In an e-mailed statement to media, Taliban spokesman Zabihullah Mujahid claimed the Islamist group had carried out the attack but said it had been on a military base and that 49 foreign and Afghan troops had been killed and wounded.
Taliban insurgents often inflate casualties inflicted on Afghan government forces and foreign troops.
Violence across Afghanistan last year reached its worst levels since the Taliban were ousted by U.S.-backed Afghan forces in 2001, with civilian and military casualties hitting record levels.
The violence underscores the challenges ahead as U.S. and NATO forces begin to hand over security responsibility to Afghan troops, allowing foreign troops to withdraw gradually from an increasingly unpopular war.
The process, announced last week, will begin with the handover of seven areas in July and culminate in the withdrawal of all foreign combat troops by 2014.