New Delhi, Nov. 21 -- Polish authorities plan to charge two Ukrainians with sabotage of a terrorist nature on behalf of Russia over an explosion that damaged a train track used for deliveries to Ukraine, prosecutors said Wednesday.

Officials said the two suspects left Poland and crossed into Belarus as soon as they committed the weekend attack on a rail line linking Warsaw with the Ukrainian border. Polish authorities allege the two Ukrainians had been collaborating with the Russian secret services for a long time.

Several others have been detained in connection to the railway explosion, prosecutors said on Wednesday. They did not provide more details.

Poland's Prime Minister Donald Tusk has described the explosion as an "unprecedented...