The police said a bomb went off just after Friday prayers as Sunni worshippers were coming out from the Ali Bin Abi Talib mosque in Baghdad's western Shurta district.
A second bomb, planted further down the street, exploded seconds later among worshippers trying to flee from the first blast. Police said the two bombings killed five people and wounded 15. Security forces quickly sealed off the area around the mosque.
Two hospital officials confirmed the casualties in the latest attacks. All officials spoke on condition of anonymity because they were not authorised to speak to reporters.
Attacks on mosques, especially Sunni ones, have increased recently and while it's possible that Sunni insurgents seeking to stoke sectarian hatred could be to blame for them, Shiite militias may also be behind the assaults.
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Today's violence comes a day after a series of attacks across Iraq left 30 people dead, most of them soldiers who were killed when two suicide bombers drove their explosive-laden cars into a military base in the town of Tarmiyah, just north of Baghdad.
But suicide attacks and large bombings, especially against Iraqi forces but also civilians, are a favourite tactic of al-Qaida's local branch.
The terror group has recently escalated its campaign of violence in order to thwart the Shiite-led government's efforts to maintain security.
Violence spiked in Iraq since a deadly security crackdown on a Sunni protest camp in April, with the pace of killing reaching levels unseen since 2008. Friday's attacks bring the death toll across the country this month to 85, according to an Associated Press count.