Militants stormed an office of Iraq's human rights ministry in northeast Baghdad on Thursday and took a number of civil servants hostage, security officials said.
The militant attack was mounted by eight armed men, police and an interior ministry official told Agence France-Presse.
Security forces sealed off the surrounding area, where several government buildings are located, including the main headquarters of the transport ministry, Al Arabiya reported.
It is not immediately clear if the attack resulted in any casualties.
The human rights ministry's spokesperson refused to comment on the incident immediately, according to AFP.
No one claimed responsibility for the attack, but Sunni militants affiliated with the al-Qaeda-linked Islamic State of Iraq and Syria, or ISIS, have in the past mounted similar armed attacks on Iraqi government buildings.
Protests broke out in Sunni Arab-majority areas of Iraq in late 2012 after the arrest of guards of then-finance minister Rafa al-Essawi, an influential Sunni Arab politician, on terrorism charges.
The arrests were seen by Iraqi Sunnis as yet another example of the Shiite-led government targeting one of their leaders.
But the demonstrations have tapped into deeper grievances, with Sunnis saying they are both marginalized by the Shiite-led government and unfairly targeted with heavy-handed tactics by security forces.
Earlier this month, Iraq hanged 26 people convicted of "terrorism" offences.
Iraq hanged at least 151 people in 2013, up from 129 in 2012 and 68 in 2011, New York-based Human Rights Watch said in its annual world report published on Jan. 21.
The United Nations human rights chief, Navi Pillay, has frequently condemned Iraq's mass executions as "obscene and inhuman," saying its justice system is deeply flawed.
Violence in Iraq has surged in the past year to its highest levels since the Sunni-Shiite sectarian bloodshed that peaked in 2006 and 2007 when tens of thousands of people were killed.