Police across US on high alert

Police in major cities across the US are on high alert after three police officers were fatally shot and three others were wounded in Baton Rouge, Louisiana on Sunday.

In New York City, America’s largest city, the New York City Police Department (NYPD) announced on Monday that all officers should patrol in pairs until further notice.

"There are to be no solo foot posts citywide," the NYPD message said. "All uniform members of service shall arrive and remain on post together. All meals and personal breaks will also be taken in pairs.”

“If the assigned post is considered integral to your command operations and you feel it should not be left unmanned during meal breaks, have that post back-filled. Police Officers on patrol should maintain a heightened level of awareness," the message said.

Police in Chicago, Illinois, and Boston, Massachusetts, were also ordered to patrol in pairs.

In Los Angeles, California, the police chief has ordered security enhancements.

The Los Angeles Police Department (LAPD) already requires all officers to work in pairs when they are on duty and responding to a call.

Police officers in New Orleans, Louisiana, were also ordered to respond to calls with at least two officers and two police divisions on the scene until further notice.

Many police agencies around the US were already on high alert following the deadly shooting of five police officers in Dallas, Texas, as well as the terrorist attack in Nice, France.

On July 7, the Federal Bureau of Investigation (FBI) issued a warning to police agencies about "threats to law enforcement and potential threats to the safety of the general public" stemming from the death of two black men in Louisiana and Minnesota.

On July 5, Alton Sterling was shot and killed after an altercation with Baton Rouge police officers. One day after Sterling’s death, Philando Castile was fatally shot by police in his car in Falcon Heights, Minnesota.

Those police killings triggered a revenge attack by a black US Army veteran who shot dead five officers in Dallas, Texas, during a protest against police brutality and racial profiling of African Americans.

The killings have renewed racial tensions that have flared repeatedly across the US since the 2014 police killing of unarmed black teen Michael Brown in Missouri.