An 18-year-old white gunman shot 10 people to death and wounded three others at a grocery store in a Black neighbourhood of Buffalo, New York, before surrendering after what authorities called an act of "racially motivated violent extremism".

Authorities said the suspect, who was armed with an assault-style rifle and appeared to have acted alone, drove to Buffalo from his home in a New York county "hours away" to launch a Saturday afternoon attack that he broadcast on the internet.

Eleven of the 13 people struck by gunfire were...