Bombs targeting Shiite Muslims and security forces in Iraq on Thursday killed 38 people and wounded 107 others in the deadliest day of violence to hit the country in more than two months.

The attacks, the worst since 76 people were killed on September 9, marked the second series of bombings against Shiites this week after three car bombs exploded near their places of worship in Baghdad on Tuesday, killing a dozen and wounding scores more.

The Thursday violence brings the number of people killed in attacks this month to at least 145 -- nine more than in October, reversing a three-month trend of declining death tolls, according to an AFP tally based on security and medical sources.

Two roadside bombs targeting a group of Shiite pilgrims in the city of Hilla killed 28 people and wounded 85 on Thursday, police and medical sources said.

Iraqi security forces cordoned off the area of the blasts and set up checkpoints in the city to search cars, an AFP correspondent said, adding that shops near the site were shuttered after the attacks.

Ali al-Khafaji, the owner of a mobile phone shop in the area of the blasts, said that there was a big explosion near a restaurant where a tent serving food to Shiite pilgrims was set up, followed by another blast when emergency personnel arrived at the scene.

In the shrine city of Karbala, a car bomb exploded under a bridge, killing five people and wounding 13, a police spokesman and a medical official said.

The spokesman said that security forces closed off all roads leading to the old city, where Imam Hussein, one of the most revered figures in Shiite Islam, is buried, and were searching for a second car bomb.

Security forces were also targeted on Thursday.

A suicide car bomb against an army patrol in Fallujah, west of Baghdad, killed three soldiers and wounded three others and four civilians, while a car bomb in Mosul in Iraq's north targeted a police patrol, killing a policeman and a civilian and wounding two more police, security and medical sources said.

Members of Iraq's security forces and the country's Shiite majority are both frequently targeted by Sunni insurgents in bomb attacks.

Millions of pilgrims flock to Karbala each year for Ashura commemorations marking Hussein's death in battle in 680 AD, which peaked on November 25 this year.

While pilgrims have often been targeted by bombings during Ashura that killed dozens, the commemorations were largely free of violence this year, though two attacks against pilgrims killed three people and wounded 35.

Pilgrims also walk from across Iraq to Karbala during the 40-day mourning period that follows Ashura.

"What happened is that security forces were in the peak of readiness and activity during the last occasion (Ashura)," but became less so after the commemorations concluded, Ali al-Haidari, an Iraqi expert in security and strategic issues, told AFP.

"Security forces usually become tired after such occasions, and the enemy benefits from this directly. In addition to that, there is also the absence of modern technologies which can detect explosives," Haidari said.

Violence in Iraq has decreased dramatically from its peak in 2006 and 2007, when brutal sectarian violence swept the country, but attacks remain common.