Dr Harith al-Dhari, secretary-general of the Association of Muslim Scholars, the highest Muslim Sunni authority in Iraq, blamed foreign powers such as Israel for the attacks. He described the attackers as those parties interested in plunging Iraq into civil war.
"Let us analyse the incident and find out who would benefit from such carnage," he said.
"No Iraqi is interested in perpetuating the state of chaos, but there are parties like the occupation and Israel interested in prolonging the period of occupation.
"They know very well that civil war would make the life of the occupiers easier in Iraq."
Shaikh Jawad al-Khalisi (Shia), imam and preacher of al-Jawadain mosque in al-Kadhimiya, has said the party who is tackling the security situation is to be blamed.
"When there is a security failure, the party responsible for security is to be blamed. And let us ask ourselves, who has the capability of launching such bombs in these circumstances?
"What story should we believe, should we believe and blame the figure that the Americans are drawing for us (Abu Musaab al-Zarqawi and al-Qaida fighters), or should we believe what we are seeing on the ground every day?" he said.
About 270 people were killed in
the Baghdad and Karbala attacks
"An Iraqi citizen would not attack a mosque, and a Muslim would not attack Muslims, these are red lines in our people's ideology," he said.
As the loudspeakers of both Sunni and Shia mosques called Iraqis to donate blood to hospitals treating people injured in the attacks on Baghdad and Karbala, Iraqis directed their anger at outsiders.
"The attacks are aimed at initiating internal conflict among the people of Iraq. But we will continue to stand united to defend our land, and we will win," said one 30-something Baghdad resident, refusing to be identified.
Another slightly older man said: "Whatever they do, they have to know that eventually, we will kick them out of our great Iraq."
And an Iraqi woman in her 40s said: "It is neither a Muslim Sunni act nor Muslim Shia, it is an American act."
US occupation authority
The US occupation authorities criticised those that hold them responsible for the attacks. US and allied military officials said Tuesday's bloody attacks on Shia in Iraq did not mean security was inadequate, but showed it was impossible to always beat determined attackers.
Brigadier General Mark Kimmitt, deputy director of operations for the US army in Iraq, said: "We certainly don't believe that this indicates the coalition is demonstrating weakness."
Dr Dhafir al-Ani, an Iraqi professor of international politics, told Aljazeera.net he believed the US forces short-changed Iraqi police by leaving them without adequate resources.
"It is true they left the security issue to Iraqis, but they did not provide them with the necessary equipment needed to preserve stability and law," he said.
"They are interested in giving the world the impression that Iraq still needs them and without their presence the country will plunge into chaos."
Political analyst Dr Mustafa al-Bazirgan, of the website Iraq-infosearch, says there are several of Iraq's neighbours interested in a chaotic Iraq.
"Some of Iraq's neighbours do not want Iraq to restore its stability. They want the US to stay engaged in a chaotic Iraq. They know if the US ended its mission in Iraq, they will be its next target."