Suspected for sheltering Osama bin Laden and al-Qeda terrorists, prior to the 9/11 attacks, he was listed as one of the most wanted terrorists by US in Federal Bureau of Investigation (FBI) since Oct, 2001. He was thought to be in Pakistan directing the Taliban troops against NATO forces and Karzai government.
Omar decided to start his movement, after a women appeared in his dream asking him to help and rise. The member's in his troops were mainly from madrassahas in Afghanistan, afghan refugee camps in Pakistan and they fought against the corruption in the civil war period. Becoming a hit, he was welcomed by the Afghans who were tired of the warlord rule.
Omar went underground after the US-UK waged a war in Afghanistan in Oct 2001.
Mohammad Hanif, a Taliban spokesman, who was captured by the Afghan authorities revealed that Omar was in Quetta, Pakistan, well protected by the Inter-Services-Intelligence (ISI), matching the accusations made by Afghanistan's President, Hamid Karzai.
After the death of Abu Musab al-Zarqawi, a militant from Jordan, Omar released a statement calling al-Zarqawi a martyr. He further reassured that nothing could stop the movements in Iraq and Afghanistan. In another statement released by Omar in Dec 2006,he said that foreign forces would be chased out from Afghanistan.
In Jan 2007, ever since he went into hiding, he made his first exchange with Muhammad Hanif, a Taliban spokesperson through emails and courier. Promising more afghan wars, he said that the bomb attacks that happened in Afghanistan the year before were carried out by the orders from the Taliban. In Apr 2007, he issued another statement supporting more suicide attacks.
The Washington Times in Nov 2009, reported that Omar moved to Karachi in Oct with the help of ISI.
Brigadier Amir Sultan Tarar, a retired Pakistani ISI officer, who had trained Omar once, said that he was ready to break his ties with al-Qeda to make peace with Afghanistan.
The Washington Post, cited from The Eclipse Group, in Jan 2011, reported that Omar suffered a heart attack on 7 Jan 2011 and and underwent treatment in hospital near Karachi. The claims were rubbished by Husain Haqqani, Pakistan's ambassador to the US.
On May 23, 2011, TOLOnews,Afghanistan, reported that unidentified sources claimed that Mullah Mohammad Omar had been killed. The reports are yet to be confirmed.