Polish police on Sunday arrested two men suspected of illegally hacking into the national railway's communications network, which destabilised traffic in some areas of the country this weekend.

"The two men arrested are Polish citizens," said Tomasz Krupa, a police spokesman in the eastern city of Bialystok where the arrest occurred.

Police also seized radio equipment from the apartment where the men, who are 24 and 29 years of age, were detained.

On Friday night, the radio communication network of the Polish PKP railway was hacked near the northwestern city of Szczecin leading to the issuing of several stop signals which brought to a standstill or delayed some 20 trains.

Traffic resumed a few hours later, according to PKP.

The attacks continued on Saturday and Sunday in other parts of the country, without posing major problems to traffic.

Media reports said the signals were interspersed with renditions of the Russian national anthem and a recording of a speech by Russian President Vladimir Putin.

Poland, a loyal ally of Ukraine, plays a key role in the transit of Western arms into the country.

The country's internal security agency said Saturday it was investigating the incident.

"We know that for some months there have been attempts to destabilise the Polish state. Such attempts have been undertaken by the Russian Federation in conjunction with Belarus," deputy coordinator of special services Stanislaw Zaryn told the PAP news agency.

The attack "did not pose risks to passengers' health or lives", he added.

During the week Polish railways saw several accidents, including two derailments, in which nobody was hurt.

Zaryn said there was no evidence to suggest those incidents and the hacking were linked.