OTTAWA -- Prime Minister Justin Trudeau is expressing sympathy over the sniper deaths of five police officers in Dallas.

In a tweet, Trudeau says Canadians are shocked by the attacks and says Canada's solidarity is with all victims of violence on this tragic week.

Snipers gunned down five Dallas police officers and wounded six others during a peaceful protest over fatal police shootings of black men in other states, police said, in bloodshed evoking the trauma of the nation's tumultuous civil rights era.

Toronto police chief Mark Saunders also tweeted out his force's heartfelt sympathies, thoughts and prayers to the Dallas police department.