An Islamic State (ISIS) agent has revealed that thousands of the jihadist group's militants are now spread all over Western nations in Europe after hiding among the thousands of refugees flooding the continent.

Speaking exclusively to BuzzFeed on the condition of anonymity, the ISIS operative from Syria claimed that more than 4,000 covert ISIS gunmen are already in place in Western European nations and just waiting for the signal to strike.

"Just wait," the ISIS smuggler said with a smile.

The ISIS agent—who claimed to be a former member of Syria's security forces—said the smuggling of jihadist militants in Europe is just the beginning of a bigger plot to avenge the U.S.-led coalition airstrikes on ISIS positions in Syria and Iraq.

"If someone attacks me then for sure I will attack them back," the smuggler said.

He said the ISIS leadership is taking advantage of Western Europe's generosity towards refugees to infiltrate the continent, noting that the refugees were welcomed warmly as they arrived in Germany this weekend after journeying through Hungary and Austria.

The ISIS operative even partly described the group's smuggling operation, saying the militants have travelled to the Turkish port cities of Izmir and Mersin to join the thousands of refugees crossing the Mediterranean headed for Italy.

He said the majority of these refugees, with ISIS militants among them, then head to friendly nations like Sweden and Germany, turning themselves over to authorities and appealing for asylum.

"They are going like refugees," he said.

The ISIS smuggler's claims were backed up by two Turkish refugee-smugglers, according to the Daily Express.

One admitted to helping more than 10 trained ISIS militants infiltrate Europe under the guise of asylum seekers.

"I'm sending some fighters who want to go and visit their families. Others just go to Europe to be ready," the unidentified Turkish smuggler said.

The Syrian jihadis said ISIS had ambitious plans. "It's our dream that there should be a caliphate not only in Syria but in all the world," he said, "and we will have it soon, God willing."

The operative said he agreed to a meeting with a BuzzFeed reporter at the urging of a former Free Syrian Army gunman who fought alongside him in the war.

The Syrian said he had been granted permission to attend the meeting by the ISIS "emir."

"There are some things I'm allowed to tell you and some things I'm not," he told the BuzzFeed interviewer.