More than one million Iraq pilgrims are gathering in the city of Karbala, south of Baghdad, to mark one of the biggest festivals in Shia Islam.
Bomb attacks on a Shia mosque and pilgrims have killed at least 13 people as Iraq's main Muslim community marks one of its biggest feasts.
The event presents a major challenge for Iraqi forces, who took charge of security just over a month ago when the US troops withdrew from Iraqi cities.
More than a million pilgrims were gathering in Karbala, south of Baghdad, to mark the birth of historic religious figure Mohammed al-Mehdi.
At least four pilgrims travelling to or from the festival have already been killed by roadside bombs.
The mosque bomb in Mosul killed 10 while a blast hit a bus returning from Karbala, killing three pilgrims.
Shia pilgrims in Karbala have often been targeted by attacks in the past.
Iraq has seen frequent sectarian strife between its Shia and Sunni Muslims.
The festival in Karbala marks the birth of Mohammed al-Mehdi, the 12th and last Shia Imam, known as the Hidden Imam.
At least three pilgrims were killed and more than eight injured when the bus in which they were travelling home from Karbala was struck by a roadside bomb as it entered Sadr City in Baghdad.
It came after an attack on Thursday evening killed at least one person making their way to the festival and injured three.
At least year's festival, at least six pilgrims were were killed by a car bomb attack in which a least 10 more were injured.
And another 18 people died when a female attacker blew herself up while among a group of pilgrims in the town of Iskandariya, south of Baghdad.
In 2007, fierce fighting in the city around the time of the festival left more than 50 people dead.
Security test
More than 20,000 Iraqi police have been deployed to protect the pilgrims gathering this year.
The car bomb late on Thursday was a reminder of the need for that protection, says the BBC's Natalya Antelava in Baghdad.
Tight security is in place around the Karbala shrines
The festival could become a test for the Iraqi government, which says its forces are in control of the situation, she adds.
But many Iraqis says the government has yet to prove it is in full control of security.
Last Friday, a series of apparently co-ordinated bombs outside five Shia mosques in Baghdad killed at least 29 people and injured more than 130.
On Tuesday, a bomb in one of Baghdad's predominantly Sunni neighbourhoods killed three people.
Are you in Iraq? Do you know someone undertaking the pilgrimage to Karbala? You can send us your experiences using the form below.
A selection of your comments may be published, displaying your name and location unless you state otherwise in the box below.
The BBC may edit your comments and not all emails will be published. Your comments may be published on any BBC media worldwide. Terms & Conditions
