Sayyaf held a registration ceremony at the Election Commission Thursday after registering to take part in the race.
Sayyaf has been backed by the leaders of both chambers of Parliament and, despite his history, is seen as a plausible contender, The Wall Street Journal reported,
His supporters chanted "Long live Islam" and "Long live jihad," the Journal reported.
"We will clean the dust off the face of the people and wipe the tears of the orphans of this country," Sayyaf said. "The first step that we need is national unity."
Many radicals, including al-Qaida founder Osama bin Laden, came to Afghanistan training camps run by Sayyaf, officials said.
Sayyaf has been described by U.S. officials as a mentor to Khalid Sheik Mohammed, planner of the Sept. 11, 2001, attacks on the United States but after attacks he sided with the United States, the report said.
Stephen Biddle, who advised the Pentagon on Afghanistan, said a victory by Sayyaf could lead to a cut in U.S. assistance to Afghanistan.