Iraq's prime minister has offered Sunni tribal fighters in Tikrit a "last chance" to abandon the Islamic State militant group.
Haidar al-Abadi was speaking on March 1 from Samarra ahead of a promised offensive to retake Tikrit, which was captured by IS militants last summer.
His office said he arrived in Samarra to "supervise the operation to liberate Tikrit from the terrorist gangs."
IS fighters control several strongholds in the mainly Sunni Muslim province of Salahuddin, including Tikrit, the hometown of executed former dictator Saddam Hussein.
A statement from Abadi's office late on March 1 announced the start of a security operation to "liberate" Salahuddin Province, though there were no initial reports of any military action under way.
Thousands of troops and fighters from Shi'ite militias known as Hashid Shaabi have been mobilized for the campaign against Islamic State in Salahuddin.
Months of U.S.-led air strikes, backed up by the Shi'ite militias, Kurdish Peshmerga fighters, and Iraqi soldiers have contained Islamic State and pushed them back from around Baghdad, the Kurdish north, and the eastern province of Diyala.
But they have held most of their strongholds in Salahuddin and taken new territory in the western province of Anbar.
Iraqi Prime Minister Haidar al-Abadi
"I call upon those who have been misled or committed a mistake to lay down arms and join their people and security forces in order to liberate their cities," Abadi said.
Analysts say Abadi's comments appear to be targeting former members of Iraq's outlawed Baath party, loyalists to Saddam Hussein, who joined the Islamic State group during its offensive, as well as other Sunnis who were dissatisfied with Baghdad's Shi'ite-led government.
Attacks by IS have sparked a new wave of bloodshed in Iraq.
In February alone, violence across Iraq killed at least 1,100 Iraqis, including more than 600 civilians, the UN Assistance Mission in Iraq said on March 1.
UN envoy Nickolay Mladenov blamed the deaths on the extremist group, government forces, and pro-government Shi'ite militias.
"Daily terrorist attacks perpetrated by ISIL continue to deliberately target all Iraqis," Mladenov said, using an alternate acronym for the Islamic State group.
"There are also concerning reports of a number of revenge killings by armed groups in areas recently liberated from ISIL," Mladenov said.
With reporting by AP and Reuters