A petrol bomb was used against police, according to witnesses who called police.
Bricks, chairs and fences were also hurled as rioters set fire to bins and smashed their way into a building, according to witnesses writing on social media.
Front gardens were ransacked and paving stones torn from the ground as crowds hunted for missiles to throw at officers.
Scotland Yard said it received reports of a petrol bomb and confirmed a number of arrests were made.
Four officers are understood to have been treated at the scene in Lambeth, Central London.
The trouble began on Halloween night when hundreds of people turned up for a suspected illegal rave in a former fire station.
More than 4,000 people said they would attend the 'Scumoween' event which was planned to go on until this morning.
The free event was due to feature music "from the full spectrum of underground dance".
Riot police, with dogs and shields, were seen drawing their batons against a crowd.