Mr Guterres planned to meet with Iraq's president, prime minister and parliament speaker before heading north to the self-ruled Kurdish region.
Guterres arrived in Iraq 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.
In a message on his arrival, the Secretary General called protection of civilians his absolute priority.
Backed by a US-led worldwide 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.
USA -backed forces are attempting to push IS fighters out of west Mosul after having liberated the less-populated eastern part of Iraq's second-largest city.
Iraqi forces have seized back most of the country's second-largest city from the Sunni hardline group in a massive six-month campaign.
"We will continue to assess and adjust our tactics to account for civilians on the battlefield while striking ISIS whenever and wherever we safely can", the colonel said.
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The offensive is part of a wider campaign launched last October to retake the entire city, which Daesh overran in mid-2014. It attributed the casualties to all sides involved in the fight for western Mosul: Iraqi and coalition airstrikes, Islamic State shellfire and improvised explosive devices detonated by the militants.
Mr Guterres said he would "focus on the dire humanitarian situation on the ground".
Having pushed the jihadists from the city's eastern section, they are now moving into the old city in western Mosul, where tens of thousands of civilians are believed to be trapped. USA officials have said they are reviewing images from more than 700 videos covering 10 days of airstrikes, along with information from human-rights groups and intelligence provided by Iraqi forces.
Huge numbers of residents have fled the fighting in west Mosul, with Iraqi authorities saying that more than 200,000 people have left the area since mid-February.
Scrocca said officials had suspicions of the tactic, and yesterday's video now provides proof and offers signs of what to look for.
Three policemen were among the dead while the rest were civilians, and a number of police were also wounded, the officials said.
As fighting with ISIL rages in west Mosul, suicide attack on security checkpoint south of Iraqi capital also wounds 60.