As of Wednesday, Ukrainian citizens can travel free by second class on the nine daily intercity trains linking the Polish cities of Warsaw, Przemysl (via Krakow) and Gdynia to the German capital Berlin and the border town of Frankfurt (Oder).

Since the Russian invasion of Ukraine on February 24 and the massive influx of refugees into Poland, PKP has put on more trains from the Ukrainian border and allowed people fleeing into the country to use them for free.

An estimated 300,000 Ukrainians have travelled into Poland that way since February 26.

Deputy Foreign Minister Pawel Szefernaker told state television on Thursday that many refugees were camping in Polish train stations, hoping to travel on to other European Union countries.

"We are working with our EU partners to facilitate this," Szefernaker said.

He said the plan concerned the "second wave" of refugees who, unlike the initial influx, did not have friends or family in Poland.

The Polish border guard service said on Thursday 1.43 million people had crossed from Ukraine to Poland since the start of the war.

Before the Russian invasion, some 1.5 million Ukrainians lived in Poland.