Five Dallas police officers have been killed and six wounded by sniper fire during protests against the shooting of black men by police, authorities say.Police are in a stand-off with one armed man in an indoor car park. Three other people have been detained.Gunfire broke out at around 20:45 local time on Thursday (01:45 GMT Friday) as demonstrators marched through the city.The protests were sparked by the deaths of Philando Castile in Minnesota and Alton Sterling in Louisiana.

Dallas Police Chief David Brown said officers remained in a stand-off with one armed man at the car park who was firing off rounds with a rifle.

He said: “The suspect that we are negotiating with has told our negotiators that the end is coming and he is going to hurt and kill more of us, meaning law enforcement, and that there are bombs all over the place in this garage and in downtown.”

Police also said officers had intercepted a car after a person threw a camouflaged bag into the back and sped off. Two occupants were being questioned.

Chief Brown said the suspects were all believed to have been working together, using rifles to carry out attacks while the rally was taking place.

He added: “We do not have a comfort level that we have all the suspects.”