Rioting youths attacked police who answered reports of a stolen vehicle being set on fire in central Belfast on Sunday night.
Officers were pelted with stones and bottles at the Westlink, a stretch of dual carriageway running through the city.
Police had gone to the area when the vehicle crashed along the dual carriageway, but then came under attack from a mob gathered at a bonfire in the nearby Devonshire area.
More than 200 nationalists, who were commemorating the internment of terrorist suspects during the Troubles, were involved, police said. Although no one was reported injured, the Westlink was closed for a time.
Sinn Féin Assembly member Fra McCann accused the PSNI of provoking trouble and of exaggerating the extent of the disturbances.
The West Belfast MLA said the police presence at a bonfire on waste ground had sparked the trouble.
"At no time were there hundreds of people involved. At its height, around a dozen young people got involved in what could be described as a mini-riot," he added.
A police commander claimed officers endured hours of attacks amid fears that guns had been brought into the area.
Chief Insp Peter Farrar said: "There was a crowd of between 200 and 300 around the bonfire and admittedly some of those people did not come out to take on the police and attack the police.
"But there was a crowd of about 100 who did come out on to the Grosvenor Road roundabout at the Westlink who were making life very difficult for the police.
"They kept on having running battles with the police for many hours throughout the night."