Officers came under attack from bottles and petrol bombs in the Lecky Road area of Derry, as they policed what has become a controversial bonfire site in recent years.
Trevor Lunn MLA said: “It is completely unacceptable for PSNI officers to be targeted in this way. They are carrying out their duty to keep the peace and protect the community and must be able to do so without hindrance.
“We must stand united with the PSNI as we seek to build a society where all traditions are respected and able to celebrate their culture. This requires the support of the Police and acceptance of their role in maintaining good order. If anyone has information about last nights incidents they should give it to the PSNI.
John Doherty, an Alliance activist in the area, added: “Those behind these attacks do not speak for the community as a whole, who will stand united against hate and intimidation.”