KABUL (Reuters) - A suicide bomber in Afghanistan killed at least 32 people and wounded more than 120 at a demonstration on Tuesday on the highway between the eastern city of Jalalabad and the main border crossing into neighboring Pakistan, officials said.

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Officials and elders said Tuesday’s attack targeted a gathering to protest against a police commander.

The blast scattered the crowd numbering hundreds of people, but more gathered after the explosion to continue the protest. The details of the complaint against the police chief were not immediately clear.

The bombing, less than a week after a suicide attack killed more than 20 people in the capital Kabul, took place as violence has flared across the nation, with heavy fighting in northern provinces.

Officials have said violence is likely to intensify before parliamentary elections next month and a presidential election in April.

There was no immediate claim of responsibility for Tuesday’s attack. The Taliban denied involvement.

Attaullah Khogyani, spokesman for the governor of Nangarhar, said 32 people were dead and 128 were wounded in the blast but Sohrab Qaderi, a member of the Nangarhar provincial council, said at least 56 bodies were taken to hospital, with 43 more wounded. That higher death toll was not confirmed.

“I feel profound indignation at this latest wave of attacks deliberately targeting civilians,” said Tadamichi Yamamoto, the senior United Nations official in Afghanistan in a statement. “The planners must face justice.”

The escalating violence has dampened hopes of peace talks to end Afghanistan’s 17-year conflict but two Taliban officials on Tuesday told Reuters the movement was preparing for another meeting with U.S. officials following one in July.

Nangarhar, one of the main strongholds of Islamic State militant fighters since early 2015, has been one of the most volatile regions this year, with a string of suicide bombings and attacks on its capital, Jalalabad.

The explosion at the protest followed a series of smaller blasts on Tuesday that targeted schools in Jalalabad and surrounding districts that were returning after summer breaks.

A 12-year-old boy was killed and several children and adults were wounded by a secondary blast that hit first responders and families rushing to the scene of the explosion.

In the northern province of Sar-e Pul, hundreds of armed men assembled to boost the city’s defenses as security forces fought to push the Taliban back from the city center, said Zabihullah Amani, the provincial governor’s spokesman.

U.S. air forces have conducted a number of strikes in northern Afghanistan as the fighting has picked up in recent days, with three strikes in Sar-e Pul on Monday, a spokesman for U.S. forces in Afghanistan said.

In addition, two air strikes were carried out in Baghlan, another northern province on Tuesday, following six the day before and U.S. advisers were on the ground supporting Afghan troops, the spokesman added.

Ghulam Mohammad Balkhi, deputy spokesman for the Afghan army’s 209 Corps, said at least 30 Taliban fighters were killed in the joint operation.