The assailants in four vehicles attacked the post in the city's Al Radhwaniya district using grenades and automatic weapons, the sources said. The army and police forces have started an operation in search of the attackers, police sources said on Monday.
Meanwhile, security sources and medics told AFP that the attack was carried out by the Daesh terror group.
There was no immediate claim of responsibility from Daesh.
Daesh attack on a lookout point west of Baghdad manned by a state-sponsored tribal force left 11 people dead late on Sunday, security sources and medics said.
The militants threw grenades and fired on the tribal Hashed forces stationed at Al Radwaniyah, on the southern outskirts of the Iraqi capital, near the Baghdad airport.
"Daesh attacked the monitoring tower, killing five members of the tribal Hashed and six local people who had come to help repel the attack," a security source said.
A medic confirmed the toll and said eight wounded were transferred to a hospital in central Baghdad.