"report riots" is correct and usable in written English.
You could use it when referring to riots that have already occurred and requires reporting, usually for information gathering or documenting. For example, "The mayor asked the police to report riots that had broken out in the town."
According to the press and official reports, riots in Muzaffarnagar started after two Hindus killed a Muslim man for stalking their female relative.
They falsely reported riots in the funeral home in Chicago.
In January 1898, Spain promised some concessions to the rebels, but when American consul Fitzhugh Lee reported riots in Havana, McKinley agreed to send the battleship USS Maine there to protect American lives and property.
According to some reports, riot police had initially been ordered to "stand and observe" rather than confront rioters.
Powell had obviously not read the local paper in Charleroi which was actually very complimentary about the English, and reported "Riot, what riot?".
A hazy but grim picture of events on Sunday and Monday night on Manus is starting to emerge, with both asylum seekers and contractors working on Manus offering first-hand accounts of the reported rioting.
According to reports, rioting began on Friday in the town of Maung Daw, spreading to state capital Sittwe and neighbouring villages.
Protests have taken place in a Chinese city for a third day, after two days of reported rioting over a land sale.
Eyewitnesses reported riot police beating the protestors and chasing stragglers into a nearby mall.
As the Associated Press is reporting, riot police used tear gas against thousands of government opponents during a nationwide "Friday of Rage" in Yemen, while in Bahrain, at least 50 people were injured -- some with gunshot wounds -- as soldiers opened fire onto government ban-defying crowds hoping to topple the monarchy.
