It was "unclear" if executions and other alleged atrocities had taken place, the senior military official told reporters, but "that's exactly what we're going to be watching" for as Iraqi forces move to secure Tikrit.
Iraqi troops backed by paramilitary groups and US-led air strikes took back Tikrit from the IS group last week.
Amnesty International said yesterday it was investigating reports of serious rights violations during the Tikrit offensive, including allegations of executions, abductions and the burning and looting of homes.
The decision to provide US-led air raids demonstrated Washington's support for the Iraqi government, the military official said.
But the Iraqis "need to understand we will hold them accountable for the aftermath of the Tikrit operation," said the official, who spoke on condition of anonymity.
The Shiite-led government in Baghdad will need to fulfill its promises to turn the city over to police, to respect the rights of Sunnis in the area and to deliver prompt humanitarian and reconstruction assistance, the official said.
The United States and rights groups have repeatedly warned that any sectarian-driven abuses will only sow the seeds of future violence and play into the hands of the IS jihadists.
