Irbil, Iraq (CNN) -- Iraqi President Fuad Masum nominated a new Prime Minister on Monday, further complicating the country's intense power struggle amid a dire humanitarian crisis and a militant threat strong enough to draw U.S. air power back to the fray. In a ceremony attended by key members of the main Shiite bloc in Parliament, Masum nominated Haider al-Abadi to succeed a defiant Nuri al-Maliki, who had earlier vowed to hang on to power. It wasn't clear what impact the situation would have on the country, which is already torn by a threat from Islamist militants so brutal that they crucify people and brag about it online.
@highlight
NEW: United States carries out airstrikes on ISIS checkpoints, vehicles
@highlight
U.S. President Barack Obama calls for an inclusive government
@highlight
Nuri al-Maliki slams the political appointment as "null and void"
@highlight
Iraqi President nominates Haider al-Abadi to replace the defiant al-Maliki
Fuad Masum
Masum
But some believe the beefed-up military presence was part of a power struggle between al-Maliki and @placeholder.
Fuad Masum
Masum
"The United States applauds President @placeholder's fulfillment of his constitutional duties and urges the Prime Minister-designate to form a government that is representative of the Iraqi people and inclusive of Iraq's religious and ethnic identities," it read.
U.S.
United States
U.S.
U.S. airstrikes against ISIS targets have dispersed the group's fighters and forced them to travel more discreetly, a @placeholder official who was not authorized to speak publicly told CNN the same day.
Iraq
Iraqi
Iraqi
The airstrikes -- authorized by President Obama last week to protect @placeholder minorities as well as U.S. personnel aiding the Iraqi army -- also appear to have at least temporarily stopped the militant advance on Irbil, the official said.
ISIS
"It's difficult to be accurate about these numbers, but initially we have reported 500 Iraqi Yazidis have died from either @placeholder direct killings or from starvation and dehydration," Amin said.