The death toll from a bomb explosion at a school in Baghdad's eastern neighborhood of Sadr City on Monday rose to 7 with 41 people injured, an Interior Ministry source said.

"The latest reports said that up to 7 students were killed and some 41 others injured by a bomb blast inside an intermediate school in Sadr City neighborhood," the source told Xinhua on condition of anonymity.

Earlier the source put the toll at 4 killed and 18 injured by the blast.

The explosion occurred before midday when a bomb hidden inside Ali Yasir intermediate school for boys in Baghdad's Sadr City neighborhood went off and caused the tragedy, the source said.

Iraqi army forces were cordoning off the scene to secure the area as ambulances and some civilian vehicles were carrying the killed to a morgue and the wounded to nearby hospitals for treatment, he added.

Sadr City is a heavily populated Shiite neighborhood and was the main stronghold for Mahdi Army militia, loyal to radical cleric Moqtada al-Sadr.

Earlier, an anonymous police source told Xinhua that a civilian was killed and five others were injured when an explosive charge attached to their car detonated while they were traveling in the Masour district in western Baghdad.

Despite the drop in violence in the last two years, recent series of attacks have raised concerns about the ability of Iraqi security forces to contain violence ahead of the country's national elections early next year.