A suicide bomber killed 20 people inside a crowded Sunni mosque north of Baghdad on Friday, police said, as Iraq struggles to contain its worst violence since 2008.
The bomber detonated explosives soon after entering the Abu Bakr al-Sadiq Mosque as the imam gave the Friday sermon in the town of Al-Wajihiyah, a police colonel said.
A doctor confirmed the toll from the blast, which also wounded 40 people.
"I was sitting near the main entrance of the mosque when a huge explosion happened," sending dirt and objects flying, said Sinan Ghalib, who later woke up in a hospital in the nearby city of Baquba with a serious wound in his left leg.
Omar Mundhir was also wounded in the leg by the explosion.
"I was sitting near the imam and the mosque was full of dozens of people when a big explosion happened, and the place went completely dark," Mundhir said, also in hospital.
"I found myself on the ground at the hospital later, with many other wounded" who were screaming and crying, he said.
Authorities slapped a curfew on Al-Wajihiyah and closed the main road from Baquba to the town after the explosion, the police colonel said.
Security forces also deployed around the hospital in Baquba where the wounded were taken.
Areas near Baquba have been hit by frequent attacks, including a bombing on Tuesday that targeted worshippers leaving a Sunni mosque in Muqdadiyah, northeast of the city, killing four people and wounding 15.
Militants have attacked both Sunni and Shiite mosques in recent months, raising fears of a return to all-out sectarian conflict that killed tens of thousands of people in past years.
A bombing targeting a Shiite religious hall in north Baghdad earlier this month killed at least 15 people.
The latest unrest brings the number of people killed in violence this month to 457, and upwards of 2,700 since the beginning of the year.
The death toll for the first 19 days of July alone has already surpassed the total for the entire month of June.
Most senior Iraqi politicians and religious leaders have remained silent about the current wave of violence.
Iraq has faced years of attacks by militants, but analysts say widespread discontent among members of its Sunni minority, which the government has failed to address, has fuelled this year's surge in unrest.
Iraqi Sunnis accuse the Shiite-led government of marginalising and targeting their community, including making unwarranted arrests and terrorism charges.
Protests that first broke out in Sunni-majority areas at the end of 2012, are still ongoing.
On April 23, security forces moved against protesters near the town of Hawijah in the north, sparking clashes that killed 53 people and sending tensions soaring.
More than 450 people have been killed each month from April to the present.
In addition to security problems, the government in Baghdad is also failing when it comes to addressing other basic issues.
Iraqis severely lack basic services, including electricity and clean water, and corruption is widespread.
Political squabbling has also paralysed the government, which has passed almost no major legislation in years.