Jürgen Stock said that the international market could be flooded by guns once the conflict ends.
“Once the guns fall silent [in Ukraine], the illegal weapons will come. We know this from many other theatres of conflict. The criminals are even now, as we speak, focusing on them,” he said.
“Criminal groups try to exploit these chaotic situations and the availability of weapons, even those used by the military and including heavy weapons.
“These will be available on the criminal market and will create a challenge. No country or region can deal with it in isolation because these groups operate at a global level.”
He added: “We can expect an influx of weapons in Europe and beyond. We should be alarmed and we have to expect these weapons to be trafficked not only to neighbouring countries but to other continents.”
Mr Stock urged Interpol members to use the organisation’s database to “track and trace” the weapons.
“We are in contact with member countries to encourage them to use these tools. Criminals are interested in all kinds of weapons … basically any weapons that can be carried might be used for criminal purposes.”
He added: “No country in our region can deal with it in isolation because the criminals I’m talking about are operating globally.”
Kyiv is set to receive further deliveries of western weapons in the coming days as Mr Zelensky’s forces seek to stem the Russian advance in the Donbas.
Britain said Thursday that it is sending sophisticated medium-range rocket systems to Ukraine. The pledge came a day after the United States and Germany said they would equip the embattled nation with advanced weapons for shooting down aircraft and knocking out artillery.