KABUL, Afghanistan (AP) — Gunmen stormed Kabul University on Monday as it hosted a book fair attended by the Iranian ambassador to Afghanistan, sparking an hourslong gunbattle at the war-torn country's largest school that saw students flee for their lives.

As the sun slowly set over the Afghan capital, details remained few though the Taliban issued a statement denying it took part in the assault as it continues peace talks with the U.S.-backed government. Those negotiations aim to help the U.S. finally withdraw from America's longest war, though daily bloodshed continues and an Islamic State affiliate launches its own attacks on Shiites in the country.

Five hours into the fighting, sporadic grenade explosions and automatic weapons fire echoed down the empty streets surrounding the university's fenced compound. Afghan troops stood guard.

"Unfortunately, there are casualties,” Interior Ministry spokesman Tariq Arian said, without elaborating. At least six people had been wounded, Public Health Ministry spokesman Akmal Samsor said hours earlier.

Ahmad Samim, a university student, told journalists he saw militants armed with pistols and Kalashnikov assault rifles firing at the school, the country's oldest with some 17,000 students. He said the attack happened at the university's eastern side where its law and journalism faculty teach.

Afghan media reported a book exhibition was being held at the university and attended by a number of dignitaries at the time of the shooting.

While Afghan officials declined to discuss the bookfair, Iran's semiofficial ISNA news agency reported Sunday that Iranian Ambassador Bahador Aminian and cultural attaché Mojtaba Noroozi were scheduled to inaugurate the fair, which would host some 40 Iranian publishers. Iranian state television reported the attack occurred, but did not offer information on its officials.

Iranian diplomats have been targeted previously by attacks in the country and nearly sparked a war between the two countries. In 1998, Iran held the Taliban responsible for the deaths of nine Iranian diplomats who were working in its consulate in northern Afghanistan and sent reinforcements to the 950-kilometer- (580-mile-) long border that Iran and Afghanistan share.

No group immediately took responsibility for the ongoing attack though the Taliban issued a statement saying they were not involved. However, suspicion immediately fell on the Islamic State group.

Last month, the Islamic State group sent a suicide bomber into an education center in the capital’s Shiite dominated neighborhood of Dasht-e-Barchi, killing 24 students and injuring more than 100. The Islamic State affiliate in Afghanistan has declared war on Afghanistan’s minority Shiite Muslims and have staged dozens of attacks since emerging in 2014.

Schools have been targeted for attacks in the past as well. Last year, a bomb outside of the Kabul University campus’ gates killed eight people. In 2016, gunmen attacked the American University in Kabul, killing 13.

Violence has been relentless in Afghanistan even as the Taliban and a government-appointed negotiation team discuss a peace agreement to end more than four decades of war in the country. The talks in Qatar have been painfully slow and despite repeated demands for a reduction in violence, the chaos has continued unabated.

A U.S. deal with the Taliban in February set the stage for peace talks currently underway in Doha. The deal also allows for the withdrawal of U.S. and NATO troops from Afghanistan.

Meanwhile Monday, a vehicle hit a roadside mine in the country's southern Helmand province, killing at least seven civilians, most of them women and children, provincial governor spokesman Omer Zwak said.

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Associated Press writers Nasser Karimi and Amir Vahdat in Tehran, Iran, contributed to this report.