A car bomb that exploded outside a private hospital in Kabul has killed 12 people and wounded another 105 people including children, according to the Afghan Ministry of Public Health.

Three victims were civilian NATO contractors and the other nine were Afghan civilians, officials said.

The bomb was placed in a Toyota sedan, a security official at the scene said.

The powerful blast destroyed several vehicles, including a school van and an armoured pick-up truck which was left twisted and blackened, with another car in flames.

Paramedics carried away casualties on stretchers.

Al Jazeera's Jennifer Glasse, reporting from Kabul, said: "The target was apparently a vehicle carrying foreign contractors." 

In a statement, the Taliban denied it was behind the attack and no other group has claimed responsibility.

"One Resolute Support contracted civilian was killed in the attack and two others died of wounds," said Brian Tribus, a spokesman for the US-led NATO mission known as Resolute Support.

Tribus did not say what nationalities the dead were.

Security sources said the contractors worked for DynCorp International, which provides training, security and aviation maintenance to the NATO mission and the Afghan military.

Increased violence

Bombings have increased in Kabul since the Taliban confirmed in July that its leader Mullah Omar had died two years ago. 

At least four people were killed at Kabul airport on August 10, while dozens of civilians were killed in multiple suicide attacks a week earlier.

The Taliban is fighting to overthrow the foreign-backed government, expel foreign forces from Afghanistan and bring in a strict interpretation of Islamic law.

The violence has stifled hopes that new leader Mullah Mansour would quickly return the armed group to the negotiating table.

Source: Al Jazeera and agencies