A gun brought to a day care centre by an eight-year-old boy accidentally went off today, wounding a seven-year-old girl in the arm, police in Germantown, Maryland said.

Authorities have linked yet another shooting to the sniper suspects – the wounding of a Maryland store clerk more than two weeks before a string of attacks began terrorising the Washington area.

Police investigations into the identity of the mystery sniper were stepped up today after a woman was shot and killed outside a shopping centre near Washington DC.