The Islamic State, or a militant group linked to it, has claimed responsibility for a suicide bombing in eastern Afghanistan on Saturday that killed at least 34 people and injured 125, according to a statement that is believed to have been sent on behalf of the Syria and Iraq-based movement.

The attack marks the first time that militants working with or inspired by the Islamic State, also known as Daesh, have claimed such a violent assault in Afghanistan. The claim could not be independently verified, but if true, it would represent the farthest from its traditional operational area of the Middle East and North Africa the group has ever targeted civilians.

The suicide bomber detonated his explosives vest in Jalalabad, the capital of the eastern province of Nangahar, outside New Kabul Bank, where Afghan government workers waited in line to collect their salaries, police officials said.

All the victims were civilians, police said.

“The suicide bomber was on foot and wanted to get inside the bank when he detonated his explosives,” said Hazrat Hussain Mashreqiwal, police spokesman for Nangahar province.

Two other bombings were reported in the city, but no additional casualties were reported. A fourth bombing took place in the Behshood district of Nangahar.

On social media, supporters of the Islamic State appeared confused by the Jalalabad attack, according to terrorism experts who follow militant activity on Twitter and other Web sites. In previous Islamic State attacks, such as an assault on the Cor­inthia Hotel in Tripoli, Libya, in January, supporters posted amateur videos, photos and Islamic State propaganda within a few hours of the violence.

Saturday’s attack could portend an even more dangerous scenario: rogue Islamic State groups that act independently, inspired by the movement, also known by the abbreviation ISIS.

“ISIS’s presence is gaining an increased ‘face’ of networks and cells across the globe, as seen in France, Morocco, Australia and Spain,” said Veryan Khan, editorial director for the Terrorism Research and Analysis Consortium, a U.S.-based research group that focuses on political violence.

“These networks plan and execute attacks without any direct instruction from the ISIS top leadership,” Khan said.

Afghan President Ashraf Ghani, though, blamed the Islamic State for Saturday’s attack, underscoring growing fears that have been swirling around the country for the past few months.

“Who claimed responsibility for the horrific attack in Nangahar today?” Ghani said to local reporters during a trip to the country’s northeastern Badakhshan province. “The Taliban did not claim responsibility for the attack, Daesh claimed responsibility for the attack.”

A statement from a group called ISIS Wilayat Khorasan that was sent to local reporters named the suicide bomber as Abu Mohammad Khorasani. A photograph said to be of the attacker showed him seated on a prayer mat, scarf covering his face, with a Kalashnikov rifle by his side and a black Islamic State flag in the background. His nationality was not mentioned.

In January, the Islamic State announced its intention to expand to Afghanistan and Pakistan and referred to the region as “Khorasan.” “Wilayat” is the Urdu word for “province.”

It was unclear whether ISIS Wilayat Khorasan is the Islamic State’s regional branch or a militant group aligned with the movement, analysts said. U.S. and Afghan military commanders have said that the Islamic State is recruiting followers and that some disgruntled Taliban factions have aligned themselves with the group.

Last year, Shahidullah Shahid, the top spokesman for the ultra-violent Pakistani Taliban — an umbrella group of various Taliban factions — announced, along with several commanders, that he had defected and pledged allegiance to the Islamic State.

On Saturday, Shahid, saying that he was the Islamic State’s spokesman in Afghanistan, apparently sent local reporters a statement claiming responsibility for the day’s attack. He congratulated the bomber on his “fidayeen,” or suicide mission.

Shahid is believed to be part of ISIS Wilayat Khorasan, but what remains unclear is whether he represents the Islamic State in Afghanistan. Shahid was unreachable for comment.

In February, the top U.S. commander in Afghanistan, Gen. John F. Campbell, while testifying before the Senate Armed Services Committee, described the Islamic State’s presence in the country as “nascent.”

His comments came three days after an American drone strike in southern Helmand province killed Mullah Abdul Rauf Khadim, a former Guantanamo Bay detainee and Taliban commander who had claimed to have aligned with the Islamic State.

Saturday’s bombing in Jalalabad was the third deadly attack in the city since April 8, when an Afghan in military uniform killed an American soldier and wounded several others in a suspected “insider attack.” That assault also killed an Afghan soldier and wounded two others. Two days later, a suicide bomber targeted a U.S. military convoy, killing four Afghan civilians and wounding 10 others. There were no U.S. casualties.

The assault on the bank was one of three separate bombing attacks that unfolded around the city at about 8.30 a.m., said Mashreqiwal, the police spokesman. The second explosion was from a bomb that detonated outside of shrine, with no casualties. The third blast was a bomb that was found unexploded outside the National Bank of Afghanistan, and police later detonated it in a controlled environment.

The fourth attack took place in the Behshood district when a small magnetic bomb killed one and wounded two others, Mashreqiwal said.

Saturday’s attack was not the first to strike Kabul Bank in Jalalabad. In 2011, a group of suicide bombers targeted the same branch, killing 38 customers who were also waiting to pick up their salaries. The Taliban claimed responsibility for that attack.

Suspicion over Saturday’s attack immediately fell on the Afghan Taliban insurgency, but the group’s spokesman, Zabiullah Mujahid, denied responsibility for any of the explosions. In a tweet, he said, “We condemn/deny involvement.”

Ehsanullah Ehsan, a spokesman for the Pakistani Taliban, also condemned the bombing in an e-mailed statement, saying killing civilians gave “a bad name to Islam.”

“No Muslim can even think of shedding the blood of innocent people,” he said.

The Pakistani government also quickly denounced the violence and expressed condolences to the victims, the latest sign of the growing rapprochement between Kabul and Islamabad.

Gen. Sher Muhammad Karimi, Afghanistan’s army chief, is in Pakistan to meet with his counter­parts and discuss border security and other issues. Afghan officials are increasingly concerned about foreign fighters who have fled a Pakistani military offensive and sought sanctuary in Afghanistan.

The Taliban and other militants have escalated their attacks in recent weeks as they enter the traditional spring offensive. Afghan President Ashraf Ghani and other officials have warned that the nation is in for a difficult spring and summer fighting the insurgency. That concern helped persuade President Obama to slow down the drawdown of roughly 10,000 U.S. military personnel remaining in the country.

On Saturday, the U.N. Assistance Mission in Afghanistan (UNAMA) condemned Saturday’s deadly attack.

“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, the U.N. secretary-general’s special representative for Afghanistan and head of UNAMA. “Those responsible for this horrendous crime must be held accountable.”

Haq Nawaz Khan in Pakistan contributed to this report.