Baghdad, Iraq (CNN) -- Iraqi forces have tightened security in and around the Shiite holy city of Karbala as tens of thousands of pilgrims pour in ahead of this weekend's culmination of a revered mourning period.
Scores of pilgrims -- who make the journey on foot -- have been killed and wounded in recent days in attacks that have been blamed on Sunni extremists, who have routinely targeted the pilgrims.
On Thursday, at least two pilgrims were killed and more than a dozen wounded in two attacks south of Baghdad, the Interior Ministry said.
In Latifiya, a roadside bomb detonated near Shiite pilgrims walking to the southern city of Karbala, killing at least one pilgrim and wounding six others, the ministry said.
In a separate attack, a parked car bomb exploded near the city of Hilla, killing at least one pilgrim and wounding 10 others, the ministry said.
The attacks coincide with a political deadlock -- which has the government divided along sectarian lines -- that is raising fears, in the wake of the U.S. military's withdrawal from Iraq, of a return to the sectarian bloodshed that nearly tore the country apart during the height of the war.
Prime Minister Nuri al-Maliki ordered security tightened following a series of attacks on pilgrims. Security forces have sealed roads and increased the number of checkpoints on the main roads leading into the city, a three-day walk south for pilgrims making their way south from Baghdad.
The pilgrimage, known as Arbaeen, marks the end of a 40-day mourning period that commemorates the seventh century death of Imam Hussein, the grandson of the Prophet Mohammed.
Hussein was killed during a battle near Karbala for control of the Muslim nation following Mohammed's death in 632. Hussein's death led to a split between Sunni and Shiite Muslims.
During Saddam Hussein's rule, the Sunni leader forbade pilgrims from making the journey on foot. He also banned some ritualistic practices.
Following the U.S.-led invasion that toppled Saddam, the pilgrimages grew in numbers.
This year's pilgrimage comes just weeks after the U.S. military pulled its troops from the country ahead of an end-of-the-year deadline to withdraw.
"We are used to bombings. It is normal for us to face that in our daily life," said Said Duraid Mohammed, a pilgrim. "And for the pilgrimage and Imam Hussein, we are ready to step on the bombs."
Another pilgrim, who identified himself as Mohammed, said he was going to Karbala in spite of the danger.
"We are going to mourn Imam Hussein, even if the terrorists bomb us and kill us," he said. "We are still going."
At least 12 people were killed and more than 50 wounded Monday in car bomb attacks on two predominantly Shiite communities in Baghdad.
On January 5, a suicide bomber struck an army checkpoint in the southern city of Nasiriya where pilgrims were gathered, an attack that killed at least 44 people and wounded 70 others.