Mullah Obaidullah, a prominent Afghan Taliban figure, reportedly died in a prison cell in Pakistan, prompting outrage from Taliban officials as to the circumstances surrounding his demise.

Moreover, it’s not clear exactly when and how he died.

The Taliban establishment reportedly informed Obaidullah’s family that he expired of a heart attack as long ago as March 2010.

It is still not clear whether the hero of Afghanistan's jihad and [the] Islamic nation passed away of sickness or he had been martyred due to torture and torment, said Zabihullah Mujahid, spokesman for the Afghan Taliban in a statement.

We strongly urge the Pakistani authorities to provide accurate and complete information regarding his detention, sickness and his death.” Obaidullah previously served as the defense minister in the Taliban government of Afghanistan prior to its overthrow in 2001 by the American military invasion.

According to reports, he was initially captured and arrested in Baluchistan in western Pakistan in 2007 and mysteriously released shortly thereafter. Under pressure from the U.S. government, Obaidullah was against re-arrested in 2008 and apparently had been detained in a prison in the southern coastal city of Karachi in Pakistan. However, Pakistani authorities have long refused to discuss his whereabouts, deepening the mystery.

The release of Obaidullah was one of many pre-conditions that the Taliban demanded from the Afghan government in exchange for agreeing to peace talks. Obaidullah was considered one of the most senior members of the Taliban, under the supreme leader Mullah Omar. He was also believed to be closely linked to Osama bin Laden, the former al-Qaeda chieftain.