St. Louis' law officers will work in pairs until further notice because of the killings of five Dallas law enforcers during a mass shooting Thursday night.

St. Louis Police Chief Sam Dotson says all officers also must wear bullet-resistant vests when on duty outside of police stations. The directive applies to St. Louis police officers, park rangers and marshals.

Authorities say gunmen killed five Dallas officers and wounded seven others during a protest over fatal police shootings of black men in other states. Dallas Police Chief David Brown blamed "snipers" and said three suspects were in custody.

A Kansas City, Missouri, Police Department spokeswoman says no Dallas-related changes are planned for Kansas City's police force, saying officers already are encouraged to wear ballistic vests on duty and be vigilant.