An Iraqi official says militants have stormed a government office in eastern Baghdad, triggering a firefight with police and a siege of the building by security forces.

Interior Ministry spokesman, Saad Maan Ibrahim, says at least six gunmen stormed the state-run Company for Transportation on Thursday morning.

Maan told state TV the police shot and killed three of the militants while the rest remain inside.

Maan says security forces managed to get most of the employees out. It was unclear if anyone remained inside the building or was taken hostage.

The brazen attack comes as Iraq is facing a stubborn insurgency in the country's western Anbar province led by a local al-Qaida branch, which seeks to undermine government efforts to maintain security ahead of national elections on April 30.