Syrian refugees are flooding into Jordan in overwhelming numbers with some 20,000 alone crossing the border this past week.

"What we have seen in terms of influx of Syrian refugees coming to Jordan is ... unprecedented, larger than any other time in the last two years. ... We have had 20,000 Syrians coming into Jordan since last Thursday," Jordanian Foreign Minister Nasser Judeh told the Reuters news agency.

Judeh attributed the recent influx of refugees to increased military activity in Syria, which has been engulfed in conflict for nearly two years since the popular uprising against President Bashar al-Assad began in March 2011.

In total, some 300,000 Syrian refugees have fled into Jordan since the conflict began, Judeh said, accounting for nearly half of all those displaced out of the country.

According to the U.N. High Commissioner for Refugees, or UNHCR, there are approximately 678,000 refugees registered or awaiting registration throughout Jordan, Turkey, Lebanon, Iraq and Egypt, though the total number of those displaced are estimated at between 1.5 million to 2.5 million.

Jordan has said that the cost of hosting the refugees amounted to $600 million in 2012, Al-Jazeera reported, and is appealing to international donors for emergency funds to build more refugee camps.

"We are making contacts with major donor countries to tell them the camps in Jordan are almost reaching full capacity, so we need help to continue building infrastructure for further camps," Judeh told Reuters.

The U.N. has also asked for additional funds to maintain its humanitarian mission in Syria, stressing that its resources have been tapped.

"We know that we've done as well as we can given the resources we've got. ... We've got no resources any more. We need money now desperately to expand this camp as well as open two others," Andrew Harper, the U.N.'s humanitarian coordinator in Jordan, said, according to the BBC.

In addition to the vast number of refugees resulting from the conflict, at least 60,000 Syrians are believed to have been killed.