Kabul, Afghanistan (CNN)A suicide bomber on a motorbike blew himself up in front of the Kabul Bank in Jalalabad early Saturday, a local government spokesman said. The ISIS terrorist group claimed responsibility for the attack. The explosion killed at least 33 people and injured more than 100 others, public health spokesman Najibullah Kamawal said. The claim appears to be the first in Afghanistan by ISIS, CNN's Nick Paton Walsh said. It was made by an offshoot called ISIS Wilayat Khorasan. In a statement, the group said the bomber was named Abu Mohammad and he belonged to their ranks. He was targeting government workers collecting their pay at the bank, the terrorists said. He detonated his charge at the peak of rush hour on the first day of the week, when the bank would be expected to be crowded. Taliban spokesman Zabiullah Mujahid, in a text message to journalists, distanced his group from the attack. "The explosion in Jalalabad doesn't have anything to do with us and we condemn it," he said. ISIS refers to Afghanistan and Pakistan as the province of "Khorasan." In March, CNN reported on ISIS recruiting in Afghanistan. The United Nations condemned the violence. "The continuing use of suicide attacks in densely populated areas, that are certain to kill and maim large numbers of Afghan civilians, may amount to a war crime," said Nicholas Haysom, head of the United Nations Assistance Mission in Afghanistan. The United Nations said that in the first three months of the year 655 people were killed and 1,155 were wounded in suicide attacks throughout the country. Fears about ISIS involvement in the region have been growing this year. In February, Mullah Abdul Rauf, a former Taliban commander who had become a recruiter for ISIS in Afghanistan, was killed in a drone strike, according to officials who spoke to CNN. And later that same week, Gen. John Campbell, the top U.S. and NATO commander in Afghanistan, told the Senate Armed Services Committee that he was concerned about the growth of ISIS in the area. "You do have some of the Taliban breaking off and claiming allegiance toward ISIS," Campbell said, attributing the phenomenon partly to a feeling of disenfranchisement on the parts of some Taliban members -- who, he said, may use ISIS tactics to gain media attention. CNN's Brian Walker, Ben Brumfield and Don Melvin contributed to this report.
U.N. says suicide attacks on mass groups of civilians may be labeled as war crimes .
Taliban condemns the attack, which ISIS took credit for .
The bomber targeted government workers picking up their pay, ISIS said in a statement .