Canada has slapped visa requirements on citizens of Mexico and the Czech Republic, citing a huge surge in refugee claims by visitors from those countries.

The change takes effect at 12:01 a.m. ET on Tuesday. For the first 48 hours, Mexicans and Czechs will be able to apply for entry on arrival in Canada. However, after 11:59 p.m. Wednesday, they must have a visa.

Mexico is now the No. 1 source of refugee claims, with the number almost tripling to more than 9,400 since 2005, the immigration department said in a release Monday. The figure represents one-quarter of all claims made.

The Czech Republic ranks second with nearly 3,000 refugee claims filed since the visa requirement for visitors from that country was lifted in October 2007. That compares with fewer than five claims in 2006, the department said.

"In addition to creating significant delays and spiraling new costs in our refugee program, the sheer volume of these claims is undermining our ability to help people fleeing real persecution," Immigration Minister Jason 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. This is unacceptable.

"The visa process will allow us to assess who is coming to Canada as a legitimate visitor and who might be trying to use the refugee system to jump the immigration queue," Kenney said. "It is not fair for those who have been waiting patiently to come to Canada, sometimes for years, when others succeed in bypassing our immigration system."

The department said the Immigration and Refugee Board accepted only 11 per cent of claims by Mexicans in 2008. It did not provide a figure for claims by Czechs.

Many of the Czech refugee claims are made by Roma alleging discrimination at home. Human rights organizations have repeatedly accused the country of discriminating against its 250,000 Roma minority.

Decision upsets Mexican, Czech authorities

In response to Canada's action, Mexico issued a release saying it regretted the decision, but gave no indication that it would require Canadian visitors to obtain visas.

However, the Czech Republic reacted strongly, with Foreign Minister Jan Kohout calling the action unprecedented against a European Union member and a war ally in Afghanistan.

Kohout indicated to The Associated Press that the Czechs are likely to impose visa requirements on Canadians travelling to the country.

Mexico said it would continue to work with Canadian authorities to deal with fraudulent refugee claims with the aim of "modifying the Canadian measure as soon as possible."

Mexican authorities blamed the rise in bogus claims on "the unrestricted operation of intermediary groups and organizations" which charge fees to assist people in making their cases.

They said the groups have taken advantage of Canada's system of assessing refugee claims, where excessive delays make it more appealing for people to file illegitimate cases.

Visitors from the two countries will have to satisfy visa officers that their visit to Canada is temporary and they won't overstay their approved time. They'll also need to have enough money to cover their stay, be in good health, have no criminal record and pose no security risk.

The department said it is working to increase its visa processing capacity in Mexico City, but the sudden imposition of the requirement will mean short-term delays in travel as resources are put in place.

It said visitors from the Czech Republic will need to submit their applications to the Canadian visa office in Vienna, Austria, which currently serves citizens from several European countries.