Tributes began pouring in from around the world soon after the shooting at a mosque in Quebec City Sunday that killed six people.

Two men were taken into custody after what Quebec Premier Philippe Couillard described as a "murderous act directed at a specific community." One is considered a suspect, and the other a witness, Quebec provincial police say.

Prime Minister Justin Trudeau called the attack "cowardly" on Twitter. He later issued a statement describing it as an act of terrorism.

Couillard called the shooting "barbaric."

Russian President Vladimir Putin sent a message to Trudeau, offering "my deep condolences in connection with the tragedy in Quebec."

"The murder of people who gathered for a prayer in a mosque is shocking by its degree of violence and cynicism," he said.

A spokeswoman for Trudeau said U.S. President Donald Trump also "offered to provide any assistance as needed.''

New York City Mayor Bill de Blasio was among the first to react to the shooting, tweeting the cities must "stand together."

The Twitter accounts for the Black Lives Matter and womens' march protest movement tweeted their solidarity with the Muslim community in Quebec City.

The City of Paris is turning off the Eiffel Tower's lights starting at midnight tonight in respect for the victims of the Quebec City mosque shooting.

Bruce A. Heyman, former U.S. ambassador to Canada, sent his condolences to the families and communities in Quebec City.

A Twitter account, purported to be run by a seven-year-old girl who recently fled Syria, also expressed support.