Iraqi police say a car bomb has exploded in a crowded bus station in the southern Shi'ite city of Karbala, killing at least 40 people and injuring more than 100 others.  In Baghdad, insurgents have attacked another of the city's bridges, killing at least 10 people. From northern Iraq, VOA's Margaret Besheer has more on the day's developments.

Emergency services flush a street after a car bomb blast in Karbala, Iraq 14 Apr 2007

The bus station is surrounded by shops, and the area was busy with morning shoppers. Police say many women and children are among the dead and injured.

This witness says he saw the explosion as he was on his way to the Imam Hussein shrine this morning.  He says many people were thrown into the air and onto the street.

This vendor in the market says he came here to sell vegetables. He says he was shocked when the blast happened, and he saw many people burning. 

Last February, an insurgent attack on a Shiite shrine in Samarra, north of the capital, pushed the country into the current phase of sectarian violence that the two-month old security plan is trying to curb. 

Karbala Governor Akeel al-Ghazali says recent intelligence indicates that the gates leading into the city could be attacked. He says he has asked the interior ministry to send more security forces to the city, but they have not arrived yet.

He adds that that the city has millions of visitors, making it impossible to check everyone. He says he lacks well-trained security forces and sophisticated bomb detection equipment.

Governor Ghazali says some Iranian pilgrims are among the victims of the attack at the bus station.  

Meanwhile, in central Baghdad's Karradah district, a suicide bomber detonated his explosives on a bridge over the Tigris River. It is the second such attack in three days.

The extent of the damage to the Jadiryah bridge was not immediately known, but police say several people on the bridge were killed in the blast.

On Thursday, a suicide truck bomber targeted the famous Sarafiya Bridge, causing heavy damage and killing eight people. The attack came hours before a suicide bomber detonated a bomb where Iraq's parliament meets in the heavily guarded Green Zone. One legislator was killed.

The latest violence deals a blow to an Iraqi and U.S. security crackdown in Baghdad and some of its surrounding provinces. Sectarian executions and kidnappings have gone down since the operation began, but high-profile bombings continue to be a problem.