Three police officers have been shot dead and up to 10 others injured by two snipers on Thursday evening (7 July) during a rally held in Dallas to protest against other police shootings in the US, according to the Dallas police department.

A video posted to Facebook shows dramatic footage in what appears to be police officers and many others lying on the street. Dallas Police Chief David Brown said in statement: "Tonight it appears that two snipers shot ten police officers from elevated positions during the protest/rally.

"Three officers are deceased, two are in surgery and three are in critical condition. An intensive search for suspects is currently underway. No suspects are in custody at this time."

The shootings happened just before 9pm local time (3am BST) according to KDFW. The news channel said that the condition of the officers is not yet known.

There were reports of several dozen gunshots. KTVT reported that police are investigating a parking garage near Commerce and Austin streets in the downtown area of Dallas and are searching for a man with a rifle.

Witnesses reported that they heard more than a dozen shots of gunfire, which scattered people. "The shots were coming from the roof," one protester told the broadcaster, adding that police officers and demonstrators alike were in line of fire.

Another witness said, "Everybody was fair game. They were just shooting randomly."

The protests were called in the wake of the shooting deaths this week of Alton Sterling in Baton Rouge, Lousiana, and Philado Castile in a Minneapolis suburb.

Castile was pulled over for a broken tail light and was shot five times as he reached for his driver's license, according to his girlfriend, Diamond Reynolds, who was in the car with him and live-streamed the aftermath of the shooting on her cell phone.