Video report by ITV News Correspondent Sally Biddulph
Six men have been killed and eight injured in a shooting at a mosque in Quebec City, Canada, in what Quebec's premier and Canada's prime minister called an "act of terrorism".
Two people have been arrested following the attack which took place in the men's section of the Quebec City Islamic Cultural Centre during Sunday evening prayers.
The suspects have been identified as French-Canadian Alexandre Bissonnette and Mohamed Khadir, of Moroccon heritage, a source told CBC News.
At least one suspect is a student at the Laval University near the mosque, the source said.
One of the suspects was arrested after he called 911 to give himself up, police said.
Six men, aged 35 to 70, are said to have died in the attack and five more are in a critical condition, police Sergeant Christine Coulombe said.
A hospital spokesman said 13 people had been discharged from hospital after receiving treatment.
Men were praying on the ground floor of the mosque while women were upstairs and it is estimated that up to 100 people were in the building at the time.
The attack comes amid heightened tensions worldwide over U.S. President Donald Trump's travel ban on certain Muslim countries.
"We condemn this terrorist attack on Muslims in a centre of worship and refuge," Trudeau said in a statement.
"It is heart-wrenching to see such senseless violence. Diversity is our strength, and religious tolerance is a value that we, as Canadians, hold dear.
"Muslim-Canadians are an important part of our national fabric, and these senseless acts have no place in our communities, cities and country," he said.
"Canadian law enforcement agencies will protect the rights of all Canadians, and will make every effort to apprehend the perpetrators of this act and all acts of intolerance."
"One of the suspects was arrested here [at the scene] and one was arrested near d'Orleans on the highway," Quebec police Sergeant Coulombe told reporters.
"There are eight people in hospital with minor or severe injuries and 39 people no injuries," she added.
Trudeau said on Twitter that he spoke to Quebec's premier and was being briefed by officials.
The prime minister said the government had offered "any & all assistance needed."
Public Safety Minister Ralph Goodale said on Twitter Sunday that he was deeply saddened by the loss of life. His office said no motive had been confirmed.
In the summer of 2016 a pig's head was left on the doorstep of the Quebec Islamic Cultural Centre.
The incident occurred in the middle of Ramadan, when Muslims fast from dawn to sunset. Practising Muslims do not eat pork.
Francois Deschamps, an organiser of a refugee-support group in Quebec City, said the motive was unknown, but right-wing groups are very organised in the area.
Deschamps said he has personally received death threats after starting a refugee support group on Facebook.
"I'm not very surprised about the event," Deschamps said.
Canada is generally very welcoming toward immigrants and all religions, but it is less so in the French-speaking province of Quebec.