Media reports from Karbala said dozens of the city's inhabitants had flocked to the governor's house, attempting to torch it but were held back by police. Residents called on the governor to resign.
Initially 50 people were killed and at least 70 were injured late Saturday when a car bomb exploded in the city's busy commercial district as worshippers were heading to evening prayers.
The casualty toll rose overnight. Many of the wounded were women and children.
The city south-west of Baghdad has the Imam Hussein and the Imam Abbas shrines, two of Shiite Islam's holiest shrines. Security was beefed up overnight, and witnesses said that US military and Iraqi army forces sealed off sensitive sites.
The Iraqi Supreme Council for Islamic Revolution, led by Abdel-Aziz al-Hakim, blamed supporters of ex-dictator Saddam Hussein and al-Qaeda for the attack, calling them "enemies of the Iraqi people."
Meanwhile, Shiite scholar Ayatollah Mohamed Taqi al-Modaresy called on the people of Karbala to form their own defences after "the failure" of the local security to protect them.
Al-Modaresy said people should form what he called "security committees" while "keeping calm, and dealing with the situation wisely."
The religious scholar also demanded that the authorities reconsider their security plan in Karbala.
Meanwhile in Sunni-dominated Adhamiya, northern Baghdad, tension continued to mount amid claims by the Association of Muslim scholars, the largest Sunni authority in Iraq, that five people were killed and 30 arrested during overnight raids by US and Iraqi forces.
The same district was a target of a mortar shells attack that killed one civilian and wounded four.
The district is a site of a massive so-called separation wall currently under construction by the US military to quell violence in the notorious Sunni district, and restrict access to residents.
Protests from both residents and Sunni hardliners followed the announcement of the construction. Iraqi and US policies towards Sunnis were questioned, and Sunni voices called the wall and the new security plan "discriminatory."
In southern Baghdad, witnesses said that four people were killed and four wounded when a mini-bus laden with explosives was detonated in al-Rabie district.
Separately, insurgents killed nine US soldiers over the past two days, according to news agency Aswat al-Iraq on Sunday, citing the US military.
Five of the soldiers were killed in Iraq's western province of al-Anbar on Friday, while four soldiers were killed Saturday in two attacks on military patrols south and south-east of Baghdad. Three soldiers were wounded in the Baghdad attacks.
The US-led coalition forces also announced Sunday that 72 terror suspects were rounded up during raids in al-Anbar and Salah al-din provinces aimed at al-Qaeda-affiliated targets. dpa abc pa sc
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