Fourteen Pakistani and Indian pilgrims have been ambushed and killed on their way to Iraq's Shia holy city of Karbala, Iraqi officials say.
It is not the first time pilgrims have been targetted south of Baghdad
The victims were taken off a bus and separated, officials said. The pilgrims were then shot dead at close range.
The motive for the attack is not clear but it comes amid increasing fears of sectarian strife in Iraq.
A US Defense Department report on Friday warned of mounting violence between the Sunni and Shia communities.
Police and hospital sources said the pilgrims were ambushed as they travelled in a bus through Anbar province in western Iraq, a stronghold of Sunni insurgents.
The attack took place some three days ago. Police say a number of women on the bus were allowed to continue to Karbala where they raised the alarm.
The victims are believed to be 11 Pakistanis and three Indians. Previous reports that 18 Iraqis had also been killed have not been confirmed.
The pilgrims reportedly had their hands and legs bound and had been shot at close range.
They were understood to be on their way to Karbala, 80km (50 miles) south of Baghdad, to the shrine of Imam Hussein, the Prophet Muhammad's grandson.
The ambush happened at a service station in the desert, about 160km (100 miles) west of Ramadi, which has been the scene of numerous killings in recent months, the BBC's James Shaw in Baghdad reports.
It is not clear what the motive for the attack was with some reports suggesting they were ambushed by robbers who stole their belongings.
An official at Karbala morgue said all the bodies bore signs of torture.
Shia pilgrims, both Iraqi and foreign, have been frequent targets for attack, and last month, gunmen opened fire on pilgrims in Baghdad, killing at least 20 people.
Pakistan has condemned the attack, and urged its citizens to avoid travelling to Iraq.
This week saw bombings and shootings that left hundreds dead.
On Thursday, suspected Sunni insurgents launched rocket and bomb attacks in mainly Shia neighbourhoods of Baghdad, killing 67 people.
Correspondents say the capital is braced for possible revenge attacks by Shia militias.
Iraq Prime Minister Nouri Maliki held talks with the country's most influential Shia cleric, Grand Ayatollah Ali al-Sistani, on Saturday to discuss the violence.
Mr Maliki went to Najaf, 160 km (100 miles) south of Baghdad, to meet the ayatollah who has previously called for an end to sectarian hatred and urged the majority Shia community to refrain from retaliation.
"If the government does not do its duty in imposing security and order to the people and protecting them, it will give a chance to other powers to do this duty and this a very dangerous matter," the cleric's office quoted him as saying.
Concern about sectarian conflict is growing in the Pentagon which issued its quarterly report on the situation in Iraq to Congress on Friday.
Since its last report, the Pentagon said, "the core conflict in Iraq changed into a struggle between Sunni and Shia extremists."
Illegal militias were becoming more entrenched, especially in Baghdad, the report said, while death squads targeting mainly Iraqi civilians were a growing problem.
Armed factions from both sides of the religious divide "are locked in mutually reinforcing cycles of sectarian strife".
While stressing that the current violence did not amount to civil war, the Pentagon's assessment said "conditions that could lead to civil war exist in Iraq, specifically in and around Baghdad."