Forty police officers have been injured and six plastic baton rounds fired as several hundred people rioted on north Belfast's Crumlin Road.
Vehicles were set on fire during the trouble
Petrol and blast bombs were thrown and a bus and 10 cars were hijacked and set on fire.
Police in riot gear were involved in a stand-off with rioters. The PSNI blamed loyalist paramilitaries.
The trouble followed the arrests of six men in connection with a loyalist feud, in which three men have been murdered.
The disturbances broke out shortly before 1730 BST when three cars and a lorry were hijacked and set on fire. The police closed off part of the Crumlin Road. A bus was also set on fire in Enfield Street.
Police on Cambrai Street came under attack from stones, bottles, fireworks and petrol bombs.
Acting PSNI Chief Inspector Paul McCormill appealed for calm.
"The serious outbreak of violent disorder is attributable to loyalist paramilitaries," he said.
Police in riot gear went to the scene
"I would appeal to those community representatives to exercise whatever influence they have over the people in the area, to ensure that this serious disorder is brought to a peaceful conclusion as soon as possible."
A "significant number" of petrol bombs, paint, bricks and stones were thrown at police, he said.
Local community workers said the disturbances broke out in direct response to the earlier searches.
There were allegations that police had been heavy-handed during the searches.
However, while local DUP representatives were raising their concerns with police, trouble broke out.
Transport company Translink said it had suspended services on the Shankill Road after the bus was hijacked.
There were no passengers on board the vehicle which was hijacked at the top of the Ballygomartin Road. The driver was not injured.
Northern Ireland's criminal justice minister David Hanson condemned the violence.
"Once again it is loyalist paramilitaries who have brought violence into loyalist areas," he said.
"The PSNI will protect the whole community and must have the support of the whole community. Those with influence must use it to bring an end to this self-destructive violence."
DUP councillor William Humphrey said his party was concerned that some police officers from the force's Tactical Support Group had been "heavy handed".
"I am challenging how some officers behaved in this community yesterday and in the last weeks," he said.
"The TSG come from other parts of Northern Ireland. They are not so concerned about maintaining community relations. They carry out their duties in a way which is a bit heavy handed."
Mr Humphrey said he had complained about what he saw in a detailed meeting with the police on Thursday and would be seeking a further meeting with senior officers.