BAGHDAD — An influential Sunni cleric was critically wounded and four of his bodyguards were killed when a bomb struck his convoy in western Baghdad on Sunday morning during one of the country’s most important holy days, according to Iraqi security officials.

The cleric, Sheik Mahdi al-Sumaidaie, is known for urging extremists within his own sect to work with the Shiite-led government; the attack highlighted the continuing dangers of taking such a position.

In recent months, Mr. Sumaidaie has served as a critical bridge between Prime Minister Nuri Kamal al-Maliki and the majority Sunni population.

On Sunday, Mr. Maliki quickly released a statement condemning the attack.

“This is another scheme from those murderers who select targets to spread sedition and silence any moderate national voice,” he said.

Sectarian tensions have intensified in recent weeks with a series of attacks that have left nearly 200 people dead, making August already one of the bloodiest months since American troops pulled out of the country in December.

Sunday’s attack took place in the capital’s Yarmouk neighborhood after the cleric had finished leading prayers at a nearby mosque in celebration of the beginning of Id al-Fitr, the Islamic festival that closes Ramadan, the holy month of daytime fasting.

Mr. Sumaidaie has publicly sided with the government against Sunni extremists, going so far as to call for a unified religious authority to help mend the rift between Sunnis and Shiites.

His statements over the past year, including a powerful December speech in which he urged Iraqis to renounce violence and warned of the possible deterioration of the country if they did not, have drawn widespread attention.

His views have also made him a target of extremist groups, and messages posted on their Web sites have condemned him by name.

Mr. Sumaidaie was not always a voice for moderation. After the American-led invasion of Iraq in 2003, he called for people to fight against the foreign forces, establishing a base for followers in a western Baghdad neighborhood. He was arrested by coalition forces, and after his release, he left the country for a long period of time.

But since the withdrawal of American troops, he returned to Iraq and has called for his followers to put down their weapons and join the government to help rebuild the country and establish security.

Yasir Ghazi reported from Baghdad, and Marc Santora from New York. (Copyright 2012 The New York Times Company 08/20/12)