OAKLAND — Efforts to stem the spike in violence and return safety and calm to besieged neighborhoods will continue unabated, police officials said Friday as they announced arrests in several killings and displayed firearms they called “weapons of war” that have been seized in connection with those cases.

Interim Chief of Police Susan Manheimer called the increase “unprecedented” and vowed to “bring safety to our neighborhoods.” Speaking to the media at police headquarters in front of a table holding 16 firearms, Manheimer said the arrests and gun seizures were part of the “incredible efforts” the department is making. She told the community, “You are not alone. We will stand with you.”