By Rob Watson BBC defence and security correspondent

There is concern over rising Islamic extremism in the region

At least 33 people have been killed and 222 injured in bomb attacks on the prime minister's office and a police station in Algeria's capital, Algiers.

Al-Jazeera television says it has received a claim of responsibility from a group recently re-named al-Qaeda Organisation in the Islamic Maghreb.

This was clearly a major attack which has shaken the capital Algiers both literally and politically and the claim comes as no surprise.

Formerly known as the Salafist Group for Prayer and Combat, it remains Algeria's most formidable and active Islamist group. If the group really is behind this attack it represents something of an escalation in tactics.

In February it targeted a number of police stations on the outskirts of Algiers and last month it bombed a bus carrying Russian workers.

Although it has also targeted individual politicians before, this would be the first large scale attack on a government building in the heart of the capital.

Morocco alert

The group, which is thought to have as many as 700 members throughout Algeria and Europe, announced it was joining forces with al-Qaeda last September.

Although its main focus is on establishing strict Islamic rule in Algeria it is now thought to harbour regional and even global ambitions since the merger with al-Qaeda.

Indeed there is growing concern among local and western security services about the rise of violent Islamic extremism across the Maghreb.

In Morocco, the security forces continue to be on high alert after three suicide bombings on Tuesday and this year has also seen arrests and foiled plots in Tunisia.

The precise extent to which violent extremism in the region is interlinked and connected to al-Qaeda is far from clear, but borders are porous and there is certainly evidence of contact between groups and individuals.