Sex traffickers are taking advantage of young women and unaccompanied children fleeing the war in Ukraine, police and volunteers in Poland have warned.

As more than a million refugees flood westwards to escape Vladimir Putin’s invading troops, a darker side to their welcome in central Europe has emerged.

Police on the border with Ukraine have made multiple arrests in the area of suspected traffickers preying on vulnerable woman and children with the promise of a lift and accommodation, sources told The Telegraph.

The authorities are understood to be particularly concerned about gangs seeking to lure vulnerable refugees to Germany for sexual exploitation.

Overwhelmed by the human tide crossing into Poland, officers are asking humanitarian volunteers at the Medyka checkpoint to demand to see proof of identities for men offering lifts to young women.

Tom Bell, one British volunteer, said: “A lot of desperate Ukrainins have gone on to Facebook or Telegram trying to hook up with people in Europe who can help them.

“Then, in a short space of time, they’re getting picked up in a car by someone they’ve never met and don’t know.

“The police have put me and other volunteers here on alert – they want us to check people’s IDs to see who they are if they’re picking up younger women, and for kids.

“We’ve been told it’s a sex trade thing.”

Mr Bell said vigilance had increased since last Thursday.

At both railway terminuses and road border crossings, there is a semi-formal network directing refugees to onward transport and accommodation.

However, there is nothing to prevent unaffiliated people stepping in to intercept the often exhausted new arrivals.