Canada has barred its soldiers from joining Ukraine’s “international brigades” of foreign fighters, amid growing concerns that captured troops could be used as Russian propaganda tools.

Speaking to Canada’s parliamentary defense committee on Wednesday, Lt. Gen. Frances Allen, deputy chief of defense staff, said top brass had issued orders preventing full-time service members and part-time reservists from traveling to join Ukraine’s newly formed foreign legion. .

The rules, which also apply to soldiers on leave, follow a call last month from Ukraine’s president, Volodymyr Zelenskiy, for volunteers to defend his country against a Russian invasion.

Thousands of people are believed to have answered, including enough Canadians to form their own battalion – the Canadian Ukrainian Brigades. While some veterans have used their skills for humanitarian work, others have taken up arms.

The only Canadian soldiers allowed to enter Ukraine are those with official approval from Wayne Eyre, chief of the defense staff, Allen said. Canada had previously sent 250 military trainers to Ukraine, but those troops were transferred to Poland before Russia invaded.

Canadian officials have long insisted they discourage travel to the region, but the foreign minister, Mélanie Joly, has previously said she sympathizes with Ukrainian Canadians who want to defend the country. Canada has the largest Ukrainian diaspora outside Russia.

“We understand that people of Ukrainian descent want to support their fellow Ukrainians and also that there is a desire to defend the homeland and in that case it is their own personal decision,” Joly said in early March. “Let me be clear: we are all very much in favor of any form of support for Ukraine at this time.”

Most of that aid is humanitarian aid, as well as arms shipments. Canada has also offered to accept an “unlimited” number of Ukrainians seeking temporary shelter.

Allen’s warning comes as Russia has threatened criminal prosecution of foreigners captured in fighting in Ukraine. Allen also told lawmakers that the captured Canadians could be a propaganda tool for Moscow as the Kremlin wants to wage its own information war amid heavy losses on the battlefield.

“Foreigners who may be involved in this country could be used in a difficult way and counterproductive to the work going on there through a disinformation campaign that we know Russia is apt to use,” he said.