The Iraqi government says it has halted a militant group's advance on Baghdad.

As The Telegraph reports, the Iraqi army started engaging the Islamic State of Iraq and Syria, or ISIS, after it made a rapid advance in which it captured the key city of Mosul.

The Telegraph adds:

"In Iraq, Maj Gen Qassim al-Moussawi, a spokesman for the military's commander-in-chief, promised to recapture all rebel-held areas, including Mosul, the nation's second city, which was overrun last Monday. The fall of the city prompted the flight of 500,000 refugees and fears that Iraq faced a return to the violence that followed the US-led invasion more than a decade ago."'Our security forces have regained the initiative,' said Maj Gen al-Moussawi, adding that the Iraqi army had won 'remarkable victories with the help of volunteers'. 'We will not stop at liberating Mosul from ISIS terrorists, but all other parts,' he continued."

Meanwhile, ISIS released photographs that allegedly show the mass killing of Shiite Iraqi soldiers.

Reporting from Beirut, NPR's Alison Meuse filed this report for our Newscast unit:

"ISIS has published dozens of photos documenting its killings. In one a masked jihadi aims his Kalashnikov at men lined up face down. The flag of the Islamic State flies in the background. Another shows a man, his mouth bound, blood streaming from his head. An Iraqi military spokesman says the ISIS photos are real."The captions are gloating. One reads: transferring hundreds of Safavid soldiers to their death. Safavid is a derogatory reference to Shiites, equating them with Persian invaders. ISIS says Shiites will pay for the repression of Nouri al-Maliki's government. Sunni soldiers are being pardoned."Meanwhile, Shiite cleric Muqtada al-Sadr is mobilizing supporters, including his feared civil-war era militia. Prime Minister al-Maliki has called for militias to support the foundering security forces."

This story will no doubt develop throughout the day. We'll update this post with the latest.

Update at 4:05 p.m. ET. U.S. Shuffles Embassy Staff:

State Department spokesperson Jen Psaki says in a statement that the U.S. is beefing up its security at its embassy in Baghdad.

"Some additional U.S. government security personnel will be added to the staff in Baghdad," Psaki said. "Other staff will be temporarily relocated – both to our Consulate Generals in Basra and Erbil and to the Iraq Support Unit in Amman."

Earlier today The New York Times reported the U.S. was getting ready to evacuate "a substantial number of its personnel" in what is the largest U.S. embassy in the world with a staff of about 5,500.

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