BAGHDAD (Reuters) - Tens of thousands of Iraqi Sunni Muslims took to the streets in Baghdad and other cities after prayers on Friday, in another show of discontent with Shi'ite Prime Minister Nuri al-Maliki.

Three weeks of mass protests reflect deep discontent among Sunnis who say Maliki's Shi'ite-led government has marginalized their minority community, increasing worries Iraq may slide back into the sectarian violence of its recent past.

Sunni unrest erupted as the war in neighboring Syria, where mostly Sunni insurgents are battling President Bashar al-Assad, an ally of Shi'ite Iran, is stirring regional tensions and testing Iraq's own fragile sectarian and ethnic balance.

(Writing by Patrick Markey; Editing by Alistair Lyon)