The incident occurred in Quebec in Canada.
Five persons have been feared dead in the attack.
Two persons have been arrested for the shooting, reports said.
The killings have taken place just after Donald Trump ordered ban on Muslims from several countries.
It suggests that racists have got emboldened after the US elections.
Later reports suggested that six persons were killed in the attack. News reports said that two suspects were held for the shootings.
UPDATE
The killer was identified as Alexandre Bissonnette, a youth with far-right views. Now he has been charged with six murders.
But will it be called Terrorism. Isn't it White Terrorism or Racist Terrorism or White supremacist Terror?
Till now, when a man even commits massacre in the West and is White, he is termed as either 'lone wolf', 'gunman', 'shooter' et al.
Media never calls him terrorist. When identity is known--that the killer is White, even media reports say, 'his motive is not killer yet' though his racist or anti-Muslim views are known by then.
READ: QUEBEC MOSQUE KILLER IDENTIFIED AS ALEXANDRE BISSONETTE
Alexandre studied Political science and anthropology.
He is a fan of French far-right leader Marine Le Pen, who is known for her anti-immigrant, anti-Muslim stand in France.
On his Facebook page, he declared his admiration for her.
Ironically, such a tragic incident --the firing at mosque, took place in adjoining Canada that has opened its gates to immigrants.
READ: MOSQUE SHOOTER A FAN OF FRENCH RIGHT WING LEADER