Shots fired in Londonderry overnight have been described as a "blatant bid to murder police officers".
In the fourth consecutive night of disorder in the city, around 16 petrol bombs and five paint bombs were thrown from the Bogside area into the Fountain estate.
Chief Inspector Neil Beck said six shots were fired at police officers close to the city's famous walls.
None of the officers were injured.
"For a fourth consecutive night police officers dealt with violence and disorder," he said.
"Around 16 petrol bombs and five paint bombs were thrown from the Bogside area into the Fountain and, in what can only be described as a blatant bid to murder police officers, shots were fired at police close to our city's walls.
"We believe that around six shots were fired striking the walls and nearby trees, however fortunately none of our officers were injured.
"Police officers should not be targeted under any circumstances and their lives should not be put in danger by simply doing their jobs, attempting to keep people safe.
"I am appealing to those with influence in the area to please assist us in trying to bring this unnecessary and unwanted violence to an end. This isn't wanted by the community and those involved are urged to cease this activity immediately."
A number of men have been charged with public order offences in connection with the disorder in recent days.
Mr Beck said he is confident that further arrests can be made.
"We have a robust strategy in place to identify those involved in the trouble of recent days and I am confident of further arrests," he said.
"Anyone with information is asked to contact us on 101."
The shots have been condemned by elected representatives.
Sinn Fein MLA for Foyle Karen Mullan said it was a "reckless and highly concerning act".
"The people of this city have already made it clear that they are completely opposed to the violence that has been taking place in the Bogside and Fountain areas this week," she said.
"So for an armed group to seek to exploit and escalate that is disgraceful. Earlier this week, we had dissidents denying involvement in orchestrating the trouble but now we see shots being fired and people are rightly asking who else would be responsible for that?"
"This was a reckless and highly concerning escalation that endangered lives. It should be condemned by all and those responsible should get off the backs of this community."
Ulster Unionist councillor Derek Hussey, who is Deputy Mayor of Derry, also expressed his disgust.
"The attempted murder of police officers in the city of Londonderry overnight is absolutely abhorrent and is to be condemned," he said.
"I am also disgusted that the Fountain estate has had to endure yet another sectarian attack on what is a small Protestant community. There is clearly a very sinister element involved.
"Some have tried to play this down as kids acting up over the summer months. That is clearly not the case. These are well orchestrated, co-ordinated attacks on the PSNI and the Fountain estate.
"I would appeal to those with influence within the republican community to do what they can to halt these attacks and to give the police their full unequivocal support."