Security is being heightened at mosques and prayer centres across the country, Muslim leaders say, in the wake of a mass shooting at a Quebec City mosque that left six people dead and injured five others on Sunday evening.

Quebec provincial police said two men have been arrested after predominantly male worshippers were shot at the Centre Culturel Islamique de Quebec (Islamic cultural centre of Quebec) in the Sainte-Foy neighbourhood in what officials are calling a “terrorist attack.”

Safwan Choudhry, the national spokesperson of Ahmadiyya Muslim Jama’at, one of the largest Muslim communities in Canada, told CTV Toronto he was in disbelief.

“Nothing like this, on this scale, has ever happened in Canada to my knowledge,” Choudhry said on Sunday night. “Never has a mosque been shot up quite like this during prayer time and during worship.”

Choudhry also said Ahmadiyya Muslim Jama’at would be heightening security at all of its mosques and prayer centres across the country.

“We’re informing members of the community to remain vigilant and to not be afraid or worried,” he said. “We’re working with authorities to ensure that these attacks don’t get replicated and more importantly members of the communities feel safe.”

The executive director of the National Council of Canadian Muslims, Ihsaan Gardee, called on Canadian law enforcement agencies to increase security around mosques and Islamic centres.

“We are horrified by this despicable act of violence," Gardee said in a statement released Monday morning. “This act of wanton murder must be punished to the fullest extent of the law.”

Patrick Lalonde, the assistant director of the Service de Police de la ville de Montreal, says security has been increased around mosques in the area. "We have asked for all our police officers to increase the levels of vigilance and surveillance around mosques and other community services," he said at a news conference Monday morning.

Gardee added that he was “heartened” by the overwhelming support for the Muslim community from fellow Canadians.

“We must unite together against divisive forces that seek to harm our communities," Gardee said.

In the same statement, Haroun Bouazzi, president of the AMAL-Quebec, a human rights group based in Montreal, said Quebec Muslims are “frightened” right now.

“We are urgently waiting for answers as to how and why such a tragedy could occur,” Bouazzi said.

Salam Elmenyawi, the president of the Muslim Council of Montreal, told CTV News Channel on Monday morning that he will be participating in discussions today about changing security measures at mosques.

“We just want to ensure that all our institutions, not only mosques but also schools and daycares, will check their security apparatus and make sure closed-circuit TVs are working and they have the necessary equipment to protect people,” Elmenyawi said.

He also suggested that employing a security guard to watch over worshippers during prayer may be an option to consider.

Mehmet Deger, the president of Dorval mosque, in Montreal's West Island, said his mosque has been targeted in nine different attacks. He said they have had graffiti, broken windows and doors, his car was shot at and he has been threatened over the phone.

“There is no way of protecting everyone from such attacks,” he told CTV News Channel on Monday. “We just believe in God and we leave the rest to him.”

Zaid Al-Rawni, of Islamic Relief Canada, an international aid and development charity, said in a statement on Sunday night that their organization had worked with the Quebec City mosque in the past. The statement said they “personally know some of the victims who have volunteered their time to help those less fortunate.”

“People were killed as they were standing in prayer,” Al-Rawni said. “Tonight we stand in solidarity with the fallen victims of this crime. We stand in hope that hate will not divide our communities.”

The statement also mentioned U.S. President Donald Trump and his executive order banning Muslims from certain countries from entering the United States.

“We don’t know anything about the attackers as yet and if this has anything to do with what’s happening in the United States,” Al-Rawni said.

The co-chair of the Centre for Israel and Jewish Affairs-Quebec (CIJA-Quebec), Rabbi Reuben Poupko, also released a statement on Sunday night to voice their solidarity with the Muslim community.

“The Jewish community is horrified by the murderous shooting at the Sainte-Foy mosque. Nothing justifies the murder of innocent civilians assembled in a place of worship,” Poupko said. “Our thoughts are with the victims and their relatives, as well as all our fellow Muslim citizens."

Another Jewish non-profit foundation, the Friends of Simon Wiesenthal Center for Holocaust Studies, also issued a statement condemning the incident.

"This tragic act of terror must be a wake-up call for all Canadians to recognize where hate and intolerance can lead," said FSWC President & CEO Avi Benlolo. "The pursuit of justice includes strengthening our laws against hate speech, and hateful acts - such as leaving a pig's head outside a mosque - intended to intimidate and threaten individuals and communities."

According to a statement from Toronto Police Services, they are watching the situation closely and say they are connected to local, national and international security agencies.

“We have people who constantly monitor for any threats against public safety in this city and we adjust our security plans whenever necessary,” the statement read.