Amid rage and grief over the death of 180 people in the coordinated blasts, US-appointed Iraqi leaders called for calm, patience and unity in the face of the gravest of provocations.
"These sick people with guns are seeking to start sectarian strife so they can consolidate their positions," Adil Abd al-Mahdi of the main Shia party, the Supreme Council for the Islamic Revolution in Iraq (SCIRI), said.
"Their aim is to stop Iraqis from winning their sovereignty," he said.
Condemnation poured in from various quarters and Shia, Sunni and Kurd members of the US-appointed Iraqi Governing Council pointed their finger at Abu Mussab al-Zarqawi, a Jordanian suspected of ties to al-Qaida.
They condemned the attacks and said they would not be deterred from creating a new democratic regime.
"The blasts did not target Iraqi Shias only. All Muslims were targeted"
Muhammad Bashar al-Faidi, Association of Muslim Scholars
The coordinated explosions in Karbala and Baghdad targeted millions of Shia worshippers commemorating the holy day of Ashura — the most important ritual in the Shia religious calendar.
It was on this day in AD 680 that al-Husayn, the grandson of Prophet Muhammad was killed in battle in Karbala.
Stung by the enormity of the latest carnage, the Association of Muslim Scholars dubbed it as an unmitigated "disaster".
"The blasts did not target Iraqi Shias only. All Muslims were targeted," said association spokesman Muhammad Bashar al-Faidi.
The mayhem the explosions left behind overwhelmed everyone. Dozens of bodies were piled in and around Karbala's main hospital as doctors struggled to treat casualties.
At least 112 people were killed in Karbala and 235 wounded in the blasts. Another 70 were killed and 321 injured when explosions targeted a mosque in the capital Baghdad.
Hundreds of people pressed against the closed gates of the hospital in Karbala, screaming for news of relatives they believed were victims.
A police officer said he saw a man blow himself up in a crowd of pilgrims outside al-Mahdi mosque.
Hours later, pilgrims wept at the mosque, where flesh was caked on a steel pole and blood stained its yellow sandstone walls. A husband washed away the blood crusted on his wife's face as she lay semi-conscious in a frayed green dress.
Baghdad witnessed similarly intense scenes. Shocked women cloaked in black robes wailed while angry men pelted stones at US-led occupation forces, blaming them for failing to prevent the attacks.