Abd al-Malek Droudkel, known as Abu Musab Abdel-Wadoud, leader of the Salafist Group for Preaching and Combat (GSPC), also urged other Islamist groups around the world to join forces to defeat the US.
"After nearly a year of contacts, we are happy to announce to the Muslin nation and our Muslim brothers the good news ... the Salafist Group for Preaching and Combat in Algeria has joined al-Qaeda organisation," Droudkel said in a statement, dated September 13, posted on GSPC website.
"After consultations, we decided to announce allegiance to Shaikh Osama bin Laden, and continue our jihad [holy war] in Algeria under his leadership."
GSPC, which has rejected a government amnesty aimed at ending years of violence, issued a statement in September 2003 in which it announced its allegiance to al-Qaeda.
The US calls GSPC the "most effective remaining armed group" and the "largest, most active terrorist organisation" in Algeria.
"The United States can be overcome only by the Islamic United States. ... We advise our brothers in other jihadist movements to join this unity. Al-Qaeda is the only organisation able to unify Mujahideens, represents the Muslim nation and speaks on its behalf," Droudkel added.
French newspaper Le Figaro on Thursday said deputy al-Qaeda leader Ayman al-Zawahiri had urged GSPC to punish "Crusader nation" France.
The daily cited a security expert who had reviewed the entire tape, released on Monday, in which al-Zawahiri called on GSPC to become "a bone in the throat of the American and French Crusaders".