Men gathered on Monday at Baghdad's biggest Sunni mosque for the funeral of one of at least 28 people, including a lawmaker, killed in a suicide attack that has been blamed on Al-Qaeda.

The blast was part of nationwide violence that left 35 dead on Sunday, just days before the conclusion of the holy Muslim fasting month of Ramadan and the Eid al-Fitr festival that marks its end.

An interior ministry official said 28 people were killed and 37 wounded in the attack late on Sunday. A defence ministry official on Monday put the toll at 30 dead and 34 wounded.

The suicide blast was quickly condemned by Prime Minister Nuri al-Maliki and parliament speaker Osama al-Nujaifi.

Among the dead were Khaled al-Fahdawi, an MP from western Anbar province allied with the Sunni-backed Iraqiya bloc, the interior ministry official said. Elderly men and children were also among the casualties.

About 40 men gathered Monday in a garden near the mosque to pray over the body of Abdel-Rizzak Mohsen al-Samarrai, a staff member of the Sunni Endowment, which is responsible for Sunni Muslim religious sites across Iraq and is based at the blue-domed Umm al-Qura mosque in west Baghdad that was targeted.

His body, which was placed in an Iraqi flag-draped coffin, was then taken for burial.

Blood stained the walls inside the mosque, while what appeared to be pieces of flesh, ceramic tiles, broken chairs and blood-soaked blankets used to carry the wounded were scattered across floor.

Baghdad security spokesman Qassim Atta and Ahmed Abdulghafur al-Samarrai, the head of Umm al-Qura and one of the founders of an anti-Qaeda militia force comprised of Sunni tribesmen in Baghdad, pointed the finger at Al-Qaeda.

"It is 100 per cent certain that Al-Qaeda is behind this attack," Atta told AFP on Monday.

He added that the bomber "blew himself up in the middle of the people in the mosque to try to get the maximum number of casualties."

Samarrai, meanwhile, told Al-Sharqiyah television: "I am sure Al-Qaeda was behind this attack... We will continue our fight against those criminals and unbelievers. They tried to drag the country into sectarian war before."

He said he had seen the attacker before at the mosque, describing him as an elderly visitor and adding: "That is why it was so easy for him to enter the mosque."

The suicide bomber walked up to a crowd, covered in bandages, as the mosque chief was giving a speech and detonated his explosives, according to Samarrai.

The death toll from the attack was the highest since August 15, when twin blasts in the southern city of Kut, also blamed on Al-Qaeda, killed 40 people.

Samarrai is known for his sermons against violent extremism. He was one of the founders of the Sahwa, or Awakening, movement in the mostly Sunni north Baghdad neighbourhood of Adhamiyah.

The Sahwa are comprised of Sunni tribesmen who joined forces with the US military against Al-Qaeda from late 2006, helping turn the tide of the insurgency.

As a result, Sahwa fighters are despised by Al-Qaeda insurgents, and Samarrai has received several threats against his life.

In addition to the Umm al-Qura attack, separate bomb and gun attacks around Iraq on Sunday killed seven other people, among them three policemen, and left 26 others wounded, according to security officials.

Meanwhile, gunmen using silenced weapons on Monday morning killed two police and one Sahwa member and wounded another policeman in an attack on a checkpoint in Baquba, north of Baghdad, a colonel in the Baquba operations command said.

And a roadside bomb in Zafraniyah in central Baghdad wounded one civilian, while another bomb in the same area targeted a police patrol, wounding three policemen and one civilian, an interior ministry official said.

The violence comes after Al-Qaeda's front group in Iraq threatened a campaign of 100 attacks, starting in mid-August, to avenge the death of Osama bin Laden in a US special forces raid in Pakistan in May.