A bomb threat targeting Muslim students forced an evacuation Wednesday of nearly 4,000 students from the downtown campus of Concordia University in Montreal.

In an email to school administrators and local media, a group identifying itself as the "underground" chapter of C4, or the Council of Conservative Citizens of Canada, at the university directly warned "Muslim students" there it would detonate one homemade explosive a day through Friday to protest their activities.

"Now that President (Donald) Trump is in office south of the border, things have changed. We will not tolerate your behavior anymore," the group said in its emailed letter, referring to the US president.

"Until Concordia University stops religious activities of all kinds on campus, we decide the following action to show how far we are ready to go to fight Muslims," the group vowed.

Montreal police said they were investigating the "threatening email." They swept the campus for explosives but found none.

A similar threatening letter was also sent to nearby McGill University, which was put on heightened alert, but it did not specify a time or place of a possible attack.

Three Concordia University buildings were evacuated just before midday, and would remain closed until around 6:00 pm (2300 GMT), Concordia spokeswoman Christine Mota said.

One of the sites was hosting an "Islam awareness week."

Quebec Universities Minister Helene David, speaking to reporters at the scene, called the threat against Muslim students "deplorable."

"We strongly denounce these attacks against a university which is a model of living together," she said.

"Quebec is an inclusive place," the minister added. "We want to live together. We will not tolerate this kind of situation."

There has been an escalation of hate crimes in the country in recent months.

In January, a white supremacist student shot dead six worshippers at a mosque in Quebec City.