BAGHDAD (AP) -- United Nations Secretary-General Antonio Guterres arrived in Iraq on Thursday amid a growing humanitarian crisis due to months-long fighting against the Islamic State group in Mosul, as the extremist group claimed responsibility for an overnight suicide attack in Baghdad.
Backed by a U.S.-led international coalition, Iraqi forces launched an operation in February to drive IS from the western half of Iraq's second-largest city, after declaring eastern Mosul "fully liberated" the previous month. The city is divided by the Tigris River into a western and eastern half and the initial operation to liberate Mosul of the extremists began last October.
Shortly after landing in Baghdad International Airport, Guterres said on Twitter that his visit is to "focus on the dire humanitarian situation on the ground." Amid reports of dozens of civilians killed by airstrikes in Mosul, he added that "protection of civilians must be the absolute priority."
Guterres planned to meet with Iraq's president, prime minster and Parliament speaker before heading north to the self-ruled Kurdish region.
Since the start of the Mosul military operation in October, more than 350,000 people have fled the fighting, according to U.N. figures. Last month, the U.S.-backed troops started a new push to recapture Mosul's western side.
The Site Intelligence group, which monitors extremist groups, reported the claim Thursday in which the IS warns Iraqi Shiites that the "flame of the battle" in Mosul will come to them in Baghdad, Karbala, and Najaf.
On Wednesday night, a suicide truck bomb targeted a police checkpoint on Baghdad's main southern entrance. Three policemen were among the dead while the rest were civilians, police and health officials said on condition of anonymity under regulations.
The militants have suffered a string of defeats over the past two years in the lead-up to the Mosul operation, but have continued to regularly launch attacks in and around Baghdad. A series of large-scale bombings claimed by IS has struck Baghdad since the operation to retake Mosul began.
Iraqi and coalition officials have repeatedly warned that after Mosul, IS will likely return to its insurgent roots as it loses more territory in both Iraq and neighboring Syria.