Unknown gunmen have attacked and seized control over an Iraqi television station reportedly killing five journalists.
The dead were Salaheddin television's chief news editor, a copy editor, a producer, a presenter and the archives manager, the officers said on Monday.
Another five employees were wounded.
Two of the attackers blew themselves up, and security forces killed the other two when they stormed the building.
Al Jazeera's Imran Khan, reporting from Erbil, said it was not clear if the journalists were executed, or killed during the crossfire.
"This is the first time that we are seeing an attack so brazen on such a civilian target," Khan said. "It's really a cause for concern here in Iraq."
Journalists have been under attack in Iraq over the last year. On December 15, gunmen shot dead television presenter Nawras al-Nuaimi in northern Iraq.
Nuaimi, who works for the Al-Mosuliyah TV, was murdered as she was walking near her home in Mosul, 400 kilometres northwest of Baghdad.
The latest attacks in Tikrit takes the number of journalists killed in Iraq to 14 in less than three months.
Mortar attack in Abu Ghraib
Other violence on Monday left at least 17 more people dead.
Mortar rounds struck an army base in the Abu Ghraib area west of Baghdad, killing a brigade commander, three other officers and two soldiers, security officials said.
Bombings and shootings in Baghdad killed at least nine people and wounded 21 on Monday, while two more people died and eight were wounded in the cities of Mosul and Baquba.
Meanwhile, defence ministry spokesman Mohammed al-Askari said Iraqi forces had destroyed two militant camps in Anbar province.
On Sunday, the United States called for regional leaders to work to cut funding and recruitment for two jihadist groups -- the Islamic State of Iraq and the Levant and Al-Nusra Front -- saying foreign fighters were going to Syria and then carrying out attacks in Iraq.
ISIL operates in both Syria and Iraq, while Al-Nusra Front is based in Syria but has also been linked to Iraq.
Washington called for "active measures to police the funding and recruitment" of the groups.
On Sunday, Prime Minister Nuri al-Maliki said a Sunni Arab anti-government protest camp in Anbar has become a "headquarters for the leadership of Al-Qaeda," calling on legitimate protesters to leave before security forces move in.
Violence in the country has reached a level not seen since 2008, when the country was emerging from a period of brutal sectarian killings.
More than 6,650 people have been killed in Iraq since the beginning of the year, according to AFP figures based on security and medical sources.