Stephen Harper says the government is looking to improve the refugee resettlement process, but it will not airlift thousands of refugees from countries such as Syria and Iraq, where extremist organizations operate, without conducting a proper security screening.

"To help, we must ensure we screen every potential refugee carefully. We have been clear that we are willing to take more people, but we must be sure we are helping the most vulnerable.

"We cannot open the floodgates and airlift tens of thousands of refugees out of a terrorist war zone without proper process. That is too great a risk for Canada," Harper said on Tuesday during a question-and-answer session on Facebook.

Harper and other world leaders have come under increased pressure to take in more refugees as the war in Syria continues to displace millions of people into neighbouring countries.

Four million Syrians have already fled the country, according to the United Nations High Commissioner for Refugees, which estimates that another 7.6 million people are displaced inside Syria.

Harper said on Tuesday, during a morning campaign stop in Mississauga, Ont., that efforts to bring in more refugees cannot come at the expense of Canada's security.

"This government has already announced prior to the latest round of headlines, we announced our intention to bring more Syrian and Iraq refugees to this country … we're looking to bring in more and we're looking to improve the process."

"When we are dealing with people that are from, in many cases a terrorist war zone, we are going to make sure that we screen people appropriately and the security of this country is fully protected," Harper said.

Conservative Party Leader Stephen Harper and his wife, Laureen, visited Facebook’s Canadian headquarters in Toronto for a Q&A session. (Facebook)

In January, the Harper government announced it would resettle 10,000 more Syrian refugees over the next three years and another 3,000 Iraqi refugees by the end of 2015, in addition to the 20,000 Iraqi refugees who have already resettled in Canada.

Harper also said Canada will continue to prioritize refugees who are ethnic and religious minorities — comments that previously drew the ire of his political rivals.

"We are going to make sure that we are selecting the most vulnerable bona fide refugees. Obviously with a focus on the religious and ethnic minorities that are the most vulnerable," Harper said during a campaign stop in Mississauga.

'Bureaucratic trap'

NDP Leader Tom Mulcair, who was in Dorval, Que., on Tuesday morning, criticized Harper for lacking the political will to take in more refugees.

"You shouldn't have people in this desperate situation falling into a bureaucratic trap asked to produce identity papers, as if you had time to renew your driver's licence when you were walking across the desert with your family.

"So you have to take that into account, having more people on the ground there would be a good idea. And, of course, we could use military assets to start moving refugees out of the area more rapidly," Mulcair said.

Over the weekend, Liberal Leader Justin Trudeau called on Harper to meet with him and the NDP leader to come up with an improved response to the crisis.

Mulcair also said he had reached out to the Conservative leader.

Harper later dismissed the proposed meeting as "partisan games."

B.C. latest province to offer help

The pressure on Harper to take in more refugees continued to mount on Tuesday when B.C. Premier Christy Clark became the fourth provincial leader in recent days to announce measures to help Syrian refugees resettle in Canada.

The photograph of the Syrian toddler Alan Kurdi, whose body was found on a beach in Turkey after he drowned with his mother and brother trying to reach Europe, hit British Columbians particularly hard because the three-year-old's aunt lives in Coquitlam.

The premiers of Nova Scotia, Quebec and Ontario also announced increased efforts to help Syrian refugees in the past week.

The Canadian office for the United Nations Refugee Agency thanked Nova Scotia Premier Stephen McNeil for his province's contribution of $50,000 for Syrian refugees.

It also expressed gratitude to individual Canadians and other groups "for the outpouring of public support and donations" offered in response to the Syrian crisis.

In a press release issued Tuesday, the United Nations High Commissioner for Refugees said the agency only had enough funds to meet about 37 per cent of its needs for the Syrian emergency.

Former Progressive Conservative prime minister Joe Clark said last week that Canada could take in refugees more quickly by sending Canadian officials to United Nations refugee camps where they could screen applicants in person.

Clark said that's what his government did when it airlifted thousands of Vietnamese applicants to Canada from refugee camps in 1979.

Agree to bring 50,000 of those frightened men, women and children to Canada. Say we'll do it by end-December. –Rick Hillier, retired Canadian general

Retired general Rick Hillier also added his voice to the debate on Sunday, urging the three main federal leaders to work together to bring 50,000 refugees to Canada by the end of the year.

"Each of our federal leaders has said we must do more, so let's do it.… Challenge our provinces, cities, churches and individual Canadians to step up and help this get done. Let's do it instead of endlessly talking about doing it," Hillier said in a post on Facebook.

Refugee applications processed 'within a year'

Part of the struggle to bring refugees to Canada is based on the resources to process them.

In 2012, Canada closed its visa processing office in Damascus, shunting hundreds of case files over to the already overstretched embassies in Jordan and Egypt.

Then, the government did deploy additional staff to try to get a handle on a case backlog that included both refugee files and family sponsorship ones — cases in which people in Canada were trying to get their own families out of the war.

But at that point, the government had made no firm commitments on Syrian refugee resettlement and staff were largely processing refugee cases belonging to Iraqis.

A spokeswoman from Citizenship and Immigration Canada told CBC News that it was "difficult" to say how many of its staff are currently assigned to processing applications from refugees, because "we move work around the immigration network depending on where we have available resources and where files can be processed most quickly."

"We are processing Syrian resettlement cases within a year and continue to look at ways to streamline processing," Nancy Caron said in an email to CBC News.

Caron said processing times depend on a number of factors, including "the volume of applications, the security situation in the region and how quickly requirements such as security screening and medical examinations can be completed."

She also noted that CIC has "reallocated resources and centralized the intake and processing of applications in Winnipeg to alleviate the administrative burden at visa offices overseas and reduce backlogs."