Related: Iraq launches security offensive in Baghdad

A suicide car bomb detonated outside the Iraqi Oil Ministry on Sunday, killing at least two security guards and wounding others. (Photo: Xinhua./AFP)

(Photo: Xinhua./AFP)

    BAGHDAD, May 29 (Xinhuanet) -- Powerful blasts and fierce gunfire were heard in western part of Baghdad on Sunday, as Iraqi security forces launched its biggest offensive against insurgents, witnesses said.

    "Iraqi soldiers and police backed by US aircraft stormed Baghdad's western districts of Amiryah, Khadra and Ghazaliyah Sunday afternoon, and fierce battles erupted between the two sides," Muwafaq Hassan, a resident in Khadra said.

    Several columns of black smoke could be seen rising over the area.

    "People are panic and hide in their homes, as many called their family members outside the area not to approach the battle zone until the clashes over," Hassan said.

    "Masked gunmen spread across Ameriyah commercial area calling on shop owners to close their shops and disappear," said Sami Hadad, another witness. "They (gunmen) also fired warning shots to prevent us from watching the battles."

    Insurgents seemed to be ready for battles with government forces in the flashpoint neighborhood of Ghazaliyah, according to residents.

    "When the Wolf Brigade entered Ghazaliyah, insurgents ambushed them almost everywhere. Sometimes they (security forces) ran away and sometimes fierce clashes broke out," Abu Sabah, a resident in the area told Xinhua.

    Earlier on Sunday, the Iraqi defense ministry said that more than 40,000 Iraqi troops took part in the offensive in Baghdad named "Operation Lightening" to crack down on a new wave of violence that has killed more than 650 people across the country since a Shiite-dominated government was formed on April 28.

    Iraqi soldiers and police blocked all entrances of Baghdad and erected some 675 checkpoints in and around the capital while others conducting a houses-to-house search. Hundreds of suspects were arrested and weapons seized, a source in the defense ministry told Xinhua on condition of anonymity.   Enditem