Iraqi insurgents launched a series of concerted attacks on security forces near Saddam Hussein’s hometown today, killing more than 20 people after Osama bin Laden again urged Muslims to wage holy war against US forces and their allies.

In one attack, heavily armed fighters took over a police station, executed the 13 policemen inside and then dynamited the building. At the same time, more gunmen attacked a police checkpoint just outside Saddam’s native town of Tikrit, north of Baghdad, and killed three officers.

Another four policeman and a national guardsmen were shot dead at a police station near Samarra, to the north, which the US military stormed in October to wrest from control of insurgents.

Three other Iraqi guardsmen were killed by a car bomb aimed at a US army convoy in the city, while a policeman was shot dead in nearby Balad while guarding a voter registration centre for January’s elections.

At least five people were killed and 22 wounded, mostly National Guards, by a suicide bomber in Baqouba who detonated his car bomb as troops helped injured from an earlier bombing.

And in Baghdad, a National Guards general survived a suicide car bomb attack as he left for work, an attack that wounded six people.

The attacks came as a new tape released in the name of bin Laden called Muslims to arms, just hours after another tape by the al-Qaeda leader anointed Abu Musab Zarqawi, the most wanted terrorist in Iraq, his "emir" in the country.

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