The group posted on its Facebook page that there would be more violence to come, and made specific threats to Baton Rouge police chief Carl Dabadie Jr.
The suspect in the Dallas gun attack told officers he was upset over recent police shootings of black men and wanted to kill white people, particularly police, according to officials.
Micah Johnson, 25, died after a stand-off with police following the attack during protests over two recent fatal police shootings of black men.
Police chief David Brown said officers killed Johnson with a robot-delivered bomb after the failure of hours of negotiations in a city-centre parking garage during which he made threats about bombs. He said Johnson told negotiators he was acting alone and was unaffiliated with any group.
We don't feel much support most days, let's not make today most days, please we need your support: Dallas police pic.twitter.com/oXRpf8m0Aj— Reuters (@Reuters) July 8, 2016
Johnson was a US army veteran. A search of his home revealed firearms, ammunition, bomb-making equipment, and a personal journal.
There were also reports last night of attacks on police in Georgia, Tennessee, and Missouri.
US President Barack Obama called the Dallas killings “a vicious, calculated, and despicable attack on law enforcement”.
The gunfire broke out as hundreds of people gathered to protest over the shooting dead of Alton Sterling in Baton Rouge, Louisiana, and Philando Castille in St Paul, Minnesota.
Sterling, 37, was shot dead on Tuesday after police pinned him to the ground. His death was filmed by two people on smartphones, and has been widely viewed online.
Castille, 34, was shot during a routine traffic stop. The aftermath of his shooting was also filmed, by his fiancée Diamond Reynolds, who said officers had asked Castille for his ID and he was just reaching for his driver’s licence. Her four-year-old daughter was in the car.
“He killed him for no reason,” Ms Reynolds said on Thursday. “He was never a bad man. He was the quietest, most laid-back person.
“Nothing in his body language said ‘intimidation’. Nothing in his body language said ‘shoot me’. Nothing in his body language said ‘kill me’.”