The official spokesman and senior strategist of the Islamic State (Isis) group was killed in northern Syria's Aleppo, the terror group, in a rare public statement, confirmed on Tuesday through their Amaq news agency.

Mohammad al-Adnani, key deputy to Isis leader Abu Bakr al-Baghdadi, was one of the world's most wanted terrorists and also the person to take over the realms of the terror group if anything happened to al-Baghdadi.

A statement from the Amaq news agency stated that al-Adnani died while supervising the group's military operations in Aleppo. The exact cause of his death was not revealed by the group and the statement said that Isis was "determined to seek revenge" for the killing.

"After a journey filled with sacrifice and fight against non-believers, the Syrian Gallant knight, Abu Mohammed al-Adnani, joined the convoy of martyr leaders... To the filthy and coward non-believers and to the holders of the Christ emblem, we bring the good news, which will keep them awake, that a new generation in the Islamic State ... that loves death more than life ... this generation will only grow steadfast on the path to Jihad, stay determined to seek revenge and be violent toward them," Isis said in the statement.

Pentagon Press Secretary Peter Cook said in a statement that al-Adnani was targeted in a "precision strike" near Al-Bab in Syria, but couldn't confirm his death.

"We are still assessing the results of the strike, but al-Adnani's removal from the battlefield would mark another significant blow to ISIS... The U.S. military will continue to prioritize and relentlessly target ISIS leaders and external plotters in order to defend our homeland, our allies and our partners, while we continue to gather momentum in destroying ISIL's parent tumor in Iraq and Syria and combat its metastases around the world," Cook's statement read.

Al-Adnani was the first to declare the Isis Caliphate even before Baghdadi did. He would direct his operatives to attack countries that are waging a war against the group. According to the Western intelligence, he commanded the Paris attacks.

Several Isis followers and members captured and questioned in the last two years have claimed that al-Adnani is head of the "Amniyat" -- the external operations unit responsible for attacks on the West.