The head of Al-Qaeda's North Africa branch, Abdelmalek Droukdel, is seen by experts as a ruthless chief who has resorted to urban fighting and introduced suicide bombings in Algeria.

The group, known officially as Al Qaeda's Branch in the Islamic Maghreb, has claimed responsibility for devastating twin car bomb attacks in Algiers on Tuesday at a UN office and in front of the Supreme Court that killed dozens.

It made the claim in a statement published on an Islamist website, the authenticity of which could not be immediately confirmed.

The 36-year-old leader, whose alias is Abou Moussaab Abdelouadoud, is said to have considered as his mentor Abu Musab Al-Zarqawi, the Jordanian-born Al-Qaeda leader in Iraq killed by the US military last year.

Algerian security forces have mobilised thousands of officers to track Droukdel, who is believed to have taken refuge in the mountains of Kabylie, east of Algiers. He has managed to evade police and the army after being surrounded several times in recent months.

He has, however, lost several high-ranking members of his group in recent clashes with authorities.

"Droukdel's strategy involves two main points: attacks with explosives and a large amount of media attention on suicide attacks," said Algerian terrorism specialist Faycal Oukaci.

His young recruits are said to have come from poor neighbourhoods.

The group has claimed several attacks in the North African country this year that have killed more than 100 people.

Targets have included the government headquarters in Algiers, barracks in Lakhdaria and Dellys, and President Abdelaziz Bouteflika's convoy in Batna.

"Droukdel wants to reinstall Islamist guerrillas in large Algerian cities, especially in the capital, Algiers, where Al-Qaeda is assured media attention," said Oukaci.

He was born in 1971 in the poor Algerian neighbourhood of Zayane in Meftah. The area had been a stronghold of a former militant organisation, the Armed Islamic Group (GIA).

Droukdel arrived at the head of what was then called the Salafist Group for Preaching and Combat in 2004, muscling his way in by brutally eliminating rivals. The group has since changed its name.

Rare photos published on the Internet have pictured him with a long, full beard, his dark eyes staring out under bushy brows. He wears a traditional robe under his military jacket, holsters across his chest, and a dark turban.

A computer specialist by training who also learned about explosives during his military service, Droukdel has put together "suicide commandos" in recent months whose members are completely committed to him, Oukaci said.

Their bedside reading is believed to include a military text written by their leader.