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Polish intelligence services are investigating a hacking attack on the country's railways, Polish media say.

Hackers broke into railway frequencies to disrupt traffic in the north-west of the country overnight, the Polish Press Agency (PAP) reported on Saturday.

The signals were interspersed with recording of Russia's national anthem and a speech by President Vladimir Putin, the report says.

Poland is a major transit hub for Western weapons being sent to Ukraine.

Saturday's incident occurred when hackers transmitted a signal that triggered an emergency stoppage of trains near the city of Szczecin, PAP reported.

About 20 trains were brought to a standstill, but services were restored within hours.

Stanislaw Zaryn, a senior security official, said Poland's internal security service ABW was investigating. "For the moment, we are ruling nothing out," he told PAP.

"We know that for some months there have been attempts to destabilise the Polish state," Mr Zaryn added. "Such attempts have been undertaken by the Russian Federation in conjunction with Belarus."

A number of Western countries have called for increased cyber-security precautions as the Ukraine conflict unfolds.

Some experts have said Russia is carrying out cyberattacks in Ukraine in an apparent attempt to test its hacking tools.

Russia has previously called such allegations "Russophobic".