Four Dallas police officers have been killed and seven wounded by sniper fire during protests against the shooting of black men by police, authorities say.
Police are in a standoff with one armed man in a garage. 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.