The death toll in a deadly bombing at a girls' school in Afghanistan has climbed to 55, many of them pupils between 11 and 15 years old, with more than 150 others wounded, Reuters reported Sunday.

Three explosions outside the school entrance struck as pupils were leaving for the day, Interior Ministry representative Tariq Arian said. The blasts took place in a mostly Shiite neighborhood west of Afghanistan's capital city of Kabul.

Video clips on television channel ToloNews showed horrific scenes, with school bags and books strewn across a blood-soaked road and smoke rising above the neighborhood as residents scrambled to help the injured. The number of deaths was expected to rise further.

"It was a car bomb blast that occurred in front of the school entrance," Reuters quoted an eyewitness as saying. He said all but seven or eight of the victims were schoolgirls going home after class.

In the capital rocked by relentless explosions, Saturday's attack was one of the worst. Outrage has grown over lack of security and mounting fears of even more similar attack as the U.S. and NATO wrap up their final military pullout from Afghanistan.

According to Afghan officials, Taliban have stepped up attacks across the country after Washington announced plans last month to withdraw all U.S. soldiers by Sept. 11.

No group has claimed responsibility for Saturday's bombing. Zabihullah Mujahid, a Taliban offiical, denied the group was involved and denounced the attack. In a message, Mujahid told reporters only the Islamic State group could be responsible for such a heinous crime.