Czech Roma say they are discriminated against and persecuted
Canada has imposed visa requirements on travellers from Mexico and the Czech Republic after a big jump in refugee claims from these two countries.
Canadian Immigration Minister Jason Kenney said there were doubts about the legitimacy of many of these claims.
Since 2007, some 3,000 Czech nationals have requested asylum, while 9,400 Mexicans applied last year.
In response, the Czech government is recalling its ambassador and is to impose visas on Canadian diplomats.
Czech Prime Minister Jan Fischer said Canada's action was unilateral and unfriendly, while the Mexican government said it regretted the move.
Announcing the new visa requirements, Mr Kenney said they were aimed at reducing the burden on Canada's refugee system.
More than half the claims by Czech nationals were abandoned or withdrawn before a final decision was made, Mr Kenney said, indicating that many claimants may not be genuine refugees. Only 11% of claims by Mexicans were accepted in 2008.
"In addition to creating significant delays and spiralling new costs in our refugee programme, the sheer volume of these claims is undermining our ability to help people fleeing real persecution," Mr Kenney said.
"All too often people who really need Canada's protection find themselves in a long line, waiting for months and sometimes years to have their claims heard."
The number of Mexicans applying has almost tripled since 2005 to 9,400 in 2008, accounting for a quarter of all claims received.
The Czech Republic is the second main source of refugee claims. Since Canada lifted visa requirements on Czech nationals in 2007, nearly 3,000 claims have been lodged, compared with just five in 2006.
Almost all the claimants are members of the Roma or gypsy minority, fleeing what they say is persecution in the Czech Republic where there has been a sharp rise in far-right extremism.
Canadian officials acknowledge that about 85% of claims by Czech nationals which are heard are accepted.
The Czech ambassador has been recalled to Prague for consultations and visa requirements are being imposed on Canadian diplomats.
The Czech Republic, as a member of the European Union, cannot unilaterally introduce visas for Canadian citizens as that would violate the EU's common visa policy.
However, Mr Fischer said Prague would be pressing other EU countries to show solidarity.
The European Commission has urged Canada to rescind its decision quickly.
The Mexican government says it will be closely monitoring the implementation of the requirements to ensure the rights of Mexicans are respected.
Officials said they had been working with Canadian authorities to try to tackle fraudulent claims.
The visa requirement came into effect on 14 July but people already travelling to Canada will be able to apply for a visa on arrival until 2359 on 15 July.