"The rise of sharia in Canada is not a coincidence. It is part of a global movement and it is a threat," said Homa Arjomand, who organised the Toronto protest.
"Women's rights are not negotiable, and we will not tolerate the interference of religion in our justice system."
In the western German city of Dusseldorf, about 25 people protested at the Canadian consulate.
'Religion is sickness'
"If the sharia is used in Canada, I also feel threatened here," said protester Nasrin Ramzanali, who said there should be a clear separation of church and state.
At the Canadian embassy in The Hague, about two dozen
people gathered to oppose the proposal.
"Religion is a sickness, and you don't open the door to invite sickness in," organiser Ebrahimi Poer said.
Some protesters were born in
Iran, where sharia is the law
"We'll keep going until this idea is scrapped, and we'll oppose the establishment of any religious court."
Demonstrations were scheduled in London, Paris, Stockholm, Goteborg, Ottawa, Montreal and Vancouver.
About 300 people rallied in front of the Ontario legislative building, some of them shouting "Shame, shame!" as Arjomand quoted Ontario Premier Dalton McGuinty's promise that sharia law in Canada would not compromise women's rights.
"Either he is naive, or he thinks people are stupid!" Arjomand said.
McGuinty has said the government will decide soon whether to allow sharia tribunals. Ontario, the most populous province in Canada, has allowed Catholic and Jewish faith-based tribunals to settle family law matters on a voluntary basis since 1991.
"Don't talk to us about sharia law, Mr. McGuinty. I am coming from a country where marital rape is protected by sharia law"
spokesman for the Federation of Iranian Refugees
The practice got little attention until Muslim leaders demanded the same rights.
Now officials in Canada - where multiculturalism is a deeply held value - must decide whether to exclude one religion, or whether they should scrap the religious family courts altogether.
That is what many demonstrators on Thursday wished for. One handmade sign demanded "Canadian laws for Canadian citizens."
Much of the rhetoric, however, focused on the oppression of women in countries where sharia is the law of the land.
"I come from Iran, where sharia has ruled for 27 years, a country that is anti-woman in the fullest sense of the word," said Mahmoud Ahmadi, spokesman for the Federation of Iranian Refugees.
"Don't talk to us about sharia law, Mr McGuinty. I am coming from a country where marital rape is protected by sharia law."
Sharia comes from several sources including the Quran, the Muslim holy book, and it governs every aspect of life.
Under most interpretations, sharia gives men more rights than women in matters of inheritance, divorce and child custody.
For example, sharia almost always grants custody of boys over age 9 and girls older than 13 to their fathers.
On the outskirts of the Toronto demonstration, pro-sharia activist Mubin Shaikh and his wife, Joanne Sijka, verbally sparred with protesters. Shaikh said the misuse of sharia does not mean it should be excluded from Canadian civil law.
"Abuse of the process is not a proof against a process, just as people wrongfully imprisoned is not a proof against Canadian law," Shaikh said.
Sijka said she trusts sharia more than she would trust Canadian courts.
"When you have a problem, you want to talk to a stranger?" she asked. "No, you want someone you know."