Iraqi police secure home made bombs, filled with TNT, after discovering suicide car and remote control device in center of Baghdad, Friday

In the latest violence to shake Iraq, separate suicide bombings have killed at least two dozen people and injured scores more.

In the worst attack, police say a car bomber detonated his explosives in a crowded market south of Baghdad, killing at least 17 people and wounding 40.

The second attack was to the north, in Tikrit. Seven police officers were killed when a bomber rammed his explosives-filled car into their minibus.

Meanwhile, in Baghdad, residents discovered at least a dozen bodies, shot execution-style and buried in a garbage dump.

And Arab satellite channel al-Jazeera reports that a previously unknown militant group has kidnapped six Jordanian contractors.  The channel also says kidnappers who are holding an Australian hostage have given his government 72 hours to start withdrawing its troops from Iraq.

Some information for this report provided by AP and AFP .