As the Iraqi government bolstered Baghdad's defenses Sunday, the Islamic militant group that captured two major cities last week posted graphic photos that appeared to show its fighters massacring dozens of captured Iraqi soldiers.
The pictures on a militant website appear to show masked fighters of the Islamic State of Iraq and the Levant, or ISIL, loading the captives onto flatbed trucks before forcing them to lie face-down in a shallow ditch with their arms tied behind their backs. The final images show the bodies of the captives soaked in blood after being shot.
The grisly images could further sharpen sectarian tensions as hundreds of Shias heed a call from their most revered spiritual leader to take up arms against the Sunni militants who have swept across the north. ISIL has vowed to take the battle to Baghdad and cities further south housing revered Shia shrines.
A car bomb meanwhile exploded in central Baghdad, killing 10 and wounding 21, according to police and hospital officials. Baghdad has seen an escalation in suicide and car bombings in recent months, mostly targeting Shia neighborhoods or security forces.
While the city of seven million is not in any immediate danger of falling into the hands of the militants, Sunday's bombing could raise tensions. Food prices in the city have risen, twofold in some cases, because of disruption to transport on the main road heading north from the capital.
The government bolstered defenses around Baghdad Sunday, a day after hundreds of Shia men paraded through the streets with arms in response to a call by Grand Ayatollah Ali al-Sistani for Iraqis to defend their country. ISIL has vowed to attack Baghdad but its advance to the south seems to have stalled in recent days.
Government officials said ISIL fighters were trying to capture the city of Tal Afar in northern Iraq on Sunday and raining down rockets seized last week from military arms depots. The officials said the local garrison suffered heavy casualties and the town's main hospital was unable to cope with the number of wounded, without providing exact numbers.
The officials spoke on condition of anonymity because they were not authorised to speak to reporters. Tal Afar is mainly inhabited by Turkmen, an ethnic minority.
Iraq's top military spokesman, Lt Gen Qassim al-Moussawi, confirmed that fighting was raging at Tal Afar, but indicated that the militants were suffering heavy casualties. On all fronts north of the capital, he said, a total of 297 militants have been killed in the past 24 hours.
There was no way to independently confirm his claims.
ISIL and allied Sunni militants captured a vast swath of northern Iraq last week, including second city Mosul and Saddam Hussein's hometown of Tikrit, as Iraqi troops, many of them armed and trained by the US, fled in disarray, surrendering vehicles, weapons and ammunition to the powerful extremist group, which also fights in Syria.
The captions of the photos say the killings were to avenge the killing of an ISIL commander, Abdul-Rahman al-Beilawy, whose death was reported by both the government and ISIL shortly before the al-Qaida splinter group's lightning offensive, which has plunged Iraq into its bloodiest crisis since the withdrawal of US troops in 2011.
"This is the fate that awaits the Shias sent by Nouri to fight the Sunnis," one caption read, apparently referring to Iraq's Shia Prime Minister Nouri al-Maliki.
Al-Moussawi, the military spokesman, confirmed the photos' authenticity and said he was aware of cases of mass murder of captured Iraqi soldiers in areas held by ISIL.
UN human rights chief Navi Pillay warned on Friday of "murder of all kinds" and other war crimes in Iraq, and said the number killed in recent days may run into the hundreds, while the wounded could approach 1,000.
Speaking in Geneva, she said her office has received reports that militants rounded up and killed Iraqi soldiers as well as 17 civilians in a single street in Mosul.
Her office also heard of "summary executions and extrajudicial killings" after ISIL militants overran Iraqi cities and towns, the statement said.
Most of the soldiers who appear in the pictures are in civilian clothes. Some are shown wearing military uniforms underneath, indicating they may have hastily disguised themselves as civilians to try to escape.
Many soldiers and policemen left their uniforms and equipment behind as the militants swept into Mosul, Tikrit and surrounding areas.
The captions did not provide a date or location, but al-Moussawi said the killings took place in Salahuddin province, the capital of which is Tikrit.
Some of the pictures appeared to show some of the soldiers pleading for their lives, others seemed terrified.
All soldiers appeared in their early 20s, with some wearing the jerseys of such European soccer clubs like Manchester United and Barcelona. Some of the militants wore black baggy pants and shirts, many of them had sandals or flip flops.