The main spokesman for the Islamic State of Iraq and the Levant (ISIL) armed group, Abu Mohamed al-Adnani, has been killed in the Syrian province of Aleppo, according to an ISIL-linked website.

Amaq, the ISIL-affiliated media outlet, said on Tuesday that Adnani was killed while monitoring military operations in Aleppo.

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Adnani, described as ISIL’s second most senior leader, has been one of the group’s longest-serving figures.

The details of Adnani’s reported death remain unclear.

Al Jazeera’s Patty Culhane, reporting from Washington DC, said there was no immediate comment or confirmation from US officials of his death.

“Sources within the Pentagon are being fairly cryptic when it comes to reports that Adnani is in fact dead,” she said.

“What they will say is that the US-led coalition launched an air strike and that they were targeting a senior official from within ISIL.”

A US defence official told Reuters news agency later on Tuesday that the US had carried out an air strike targeting Adnani. The US official said Tuesday’s strike targeted a vehicle in the Syrian town of al-Bab but declined to say whether Adnani was killed.

Al Jazeera’s Culhane said Adnani has been a priority target for the US.

“In 2015, they put out a list of four names; they said these were top four officials they wanted information on – and he was on that list,” she said.

“They officially declared him a terrorist and put a $5m bounty on any information that would lead to his capture.”

‘Voice of ISIL’

Adnani has been the voice of ISIL, also known as ISIS, over the past few years, and has released numerous, lengthy audio files online in which he urged followers to carry out attacks.

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Earlier this year, he called for massive attacks during the Muslim holy month of Ramadan. He has also called for attacks in Western countries.

Saad Jawad, a Middle East analyst and professor of political science, told Al Jazeera that if Adnani’s death was confirmed, it would be a “very significant” development.

“Although he was declared as the spokesman of ISIL, in reality he was the real ruler of the ISIL parts in Syria. He’s a Syrian. He was born in Idlib,” Jawad said.

Adnani was responsible for many of ISIL’s “very aggressive operations”, he said.

“He was even tipped as the one who was supporting all activities or encouraging activities in Europe,” he added.

In 2000, Adnani declared allegiance to al-Qaeda in Iraq leader Abu Musab al-Zarqawi.

He later spent three years in jail, and in 2011 ISIL leader Abu Bakr al-Baghdadi sent him to fight in Syria.

ISIL controls large swaths of territory in Syria and Iraq, and is fighting Syrian troops, US-backed fighters and other rebel groups in both countries.

Source: Al Jazeera News and agencies