Shaikh Muhammad Mahdi al-Khalissi has issued a statement, obtained by Aljazeera.net on Sunday, condemning the US assault on Falluja and describing it as "aggression and dirty war".
"No matter how powerful the occupation forces are, they will be driven out of Iraq sooner or later," he said.
"The current savage military attack on Falluja by US occupation forces and the US-appointed Iraqi government is an act of mass murder and a crime of war."
Al-Khalissi said he and his faction fully supported the religious decree issued by Iraq's influential Sunni Muslim authority, the Association of Muslim Scholars, in which it prohibited Iraqis from participating in the US attack on Falluja.
Cycle of aggression
Another Shia scholar and member of the Islamic Movement in Iraq, Shaikh Hadi al-Khalissi, has condemned the attack on Falluja, labelling it a chapter in the cycle of aggression against Iraqis and the Muslim nation.
Tens of thousands of Fallujans
left the city prior to the attack
"Everything happening on the ground in Iraq now is part of a plan to destroy Iraq and Islam," he told Aljazeera.net.
Shaikh Hadi accused the US authorities in Iraq of orchestrating the assault on Falluja in a bid to keep all of Iraq in chaos.
"This occupation is based on Zionist motivations. Its first aim is to destroy the state of Iraq, which has always resisted the hegemony of Zionism," he said.
"I can assure you they do not want to build the country. They do not carry any good intention. All that they want is a weak Iraq that cannot rise against Israel."
Shia and Sunni
Al-Khalissi stressed that a peaceful solution could be achieved in every Iraqi-Iraqi disagreement if Iraqis were left alone.
"As long as the occupation exists on Iraq's national soil, chances of a peaceful solution will always be weak, because the occupation cannot afford harmony among Iraqis," he said.
"I am here today as a Shia figure belonging to a prominent Shia religious family to confirm that Iraqi Sunni Muslims are our brothers and dear countrymen. We lived since the dawn of Islam in this country as brothers.
"We back our brotherly Sunni Muslims in the city of Falluja and nothing on earth will spoil our brotherhood with them."
Al-Khalissi's family historically dominates al-Kadhimiya mosque and religious school in Baghdad where Imam Musa al-Kadhim, a descendant of Prophet Muhammad regarded by Shia Muslims as one of their 12 imams, is buried.
The family is known for resisting foreign domination. Grand Shaikh Muhammad al-Khalissi was one of the key leaders of the 1920 revolution against the British occupation of Iraq. The revolution paved the way for Iraq's independence in 1921.
For its part, the movement of the Iraqi Muslim Shia leader Muqtada al-Sadr said it had suspended its support for the forthcoming election in January 2005.
Shaikh Ali Smaysim, an aide to the Shia leader, told Aljazeera.net that al-Sadr's movement suspended its participation in the election in protest against the brutalities inflicted on Falluja and other Iraqi towns.
"I am here today as a Shia figure belongs to a prominent Shia religious family to confirm that Iraqi Sunni Muslims
are our brothers and dear countrymen"
Shaikh Hadi al-Khalissi,
Iraqi Islamic Movement member
"This level of military power against Iraqi cities will result in preventing many Iraqi cities from participating in the coming elections, and that is against the standards of clean and honest elections," Shaikh Smaysim said.
"There has been a chance for a peaceful solution, but the government always chooses the military solution because the US wants that."